WEBVTT 00:00:00.000 --> 00:00:01.320 INSTRUCTOR: Single-case design. 00:00:01.320 --> 00:00:05.380 This is probably one of the most common types of quasi-experimental designs, 00:00:05.380 --> 00:00:08.980 and sometimes it gets a little confused with case studies for obvious reasons. 00:00:08.980 --> 00:00:11.545 It includes single case design. 00:00:11.545 --> 00:00:13.520 It sounds like a case study. 00:00:13.520 --> 00:00:15.380 But unlike a case study, 00:00:15.380 --> 00:00:17.980 so case studies usually just describe people. 00:00:17.980 --> 00:00:23.090 There's no real manipulation or experiment going on, 00:00:23.090 --> 00:00:25.820 there's no exposure to some type of stimulus, 00:00:25.820 --> 00:00:27.430 and then to measure a reaction. 00:00:27.430 --> 00:00:29.160 So with an actual case study, 00:00:29.160 --> 00:00:30.860 you're just following them in their life, 00:00:30.860 --> 00:00:33.460 seeing how they react normally to things, 00:00:33.460 --> 00:00:36.450 and describing that very special case. 00:00:36.450 --> 00:00:38.190 With a single-case design, 00:00:38.190 --> 00:00:39.765 again, this is quasi-experimental, 00:00:39.765 --> 00:00:43.515 you are looking at manipulating them in some way oftentimes. 00:00:43.515 --> 00:00:47.265 How does someone with depression react to this type of therapy? 00:00:47.265 --> 00:00:52.380 Or how does a pack-a-day smoker react to this type of medication or treatment? 00:00:52.380 --> 00:00:56.790 Again, you are running a type of experiment, it's a quasi-experiment. 00:00:56.790 --> 00:01:00.135 You're not just following these people around and recording their everyday lives, 00:01:00.135 --> 00:01:02.340 you're trying to change them in some way, 00:01:02.340 --> 00:01:06.255 usually, or treat them is maybe a better way of saying it. 00:01:06.255 --> 00:01:10.740 Also, single case, and this is where I don't like the way this is named— 00:01:10.740 --> 00:01:14.990 it's misleading—it implies that you're following one person. 00:01:14.990 --> 00:01:19.000 That's really never the case with a single-case design. 00:01:19.000 --> 00:01:22.330 The reason why we do call it a single-case design is because 00:01:22.330 --> 00:01:26.190 we're usually analyzing data on an individual basis. 00:01:26.190 --> 00:01:30.180 Pretty much all the analyses that we've been doing so far have been on group levels. 00:01:30.180 --> 00:01:32.530 Comparing group averages, seeing if there's 00:01:32.530 --> 00:01:35.595 a correlation between two variables on average. 00:01:35.595 --> 00:01:38.300 The difference with a single-case design is you're 00:01:38.300 --> 00:01:41.615 measuring change in individuals over time. 00:01:41.615 --> 00:01:48.440 You often hear things like two out of three people benefited from this therapy. 00:01:48.440 --> 00:01:52.025 Well, that's a quasi-experimental single-case statement. 00:01:52.025 --> 00:01:54.320 You're measuring things on an individual basis. 00:01:54.320 --> 00:01:57.020 You're not saying, on average, people got 30% better, 00:01:57.020 --> 00:02:00.380 you're saying two out of three people got better. 00:02:01.610 --> 00:02:05.095 I'm going to talk about one of the most common types of 00:02:05.095 --> 00:02:09.745 single-case designs which involves some type of pre-post measure. 00:02:09.745 --> 00:02:13.830 Usually, you're measuring the DV at a baseline. 00:02:13.830 --> 00:02:15.860 I'll go and put this up at a baseline period. 00:02:15.860 --> 00:02:18.530 We call that baseline because it's before manipulation, 00:02:18.530 --> 00:02:20.040 it's just the regular level. 00:02:20.040 --> 00:02:21.920 Then after the manipulation, 00:02:21.920 --> 00:02:23.600 usually what we call a treatment period, 00:02:23.600 --> 00:02:27.935 because some type of treatment or effect has been undertaken. 00:02:27.935 --> 00:02:29.820 A real classic one, 00:02:29.820 --> 00:02:31.650 one that's received a lot of interest lately as 00:02:31.650 --> 00:02:36.210 a possible treatment for depression is called deep brain stimulation. 00:02:36.210 --> 00:02:40.350 This is like having a pacemaker attached to your brain. 00:02:40.350 --> 00:02:42.330 In a real way, it really is like that. 00:02:42.330 --> 00:02:46.365 You have a pacemaker battery-like device implanted behind your collarbone, 00:02:46.365 --> 00:02:49.630 and then electrodes go into very deep centers of your brain, 00:02:49.630 --> 00:02:52.845 especially in the limbic system where depression is thought to originate. 00:02:52.845 --> 00:02:57.040 These deep brain stimulations actually shut down 00:02:57.040 --> 00:03:01.495 or calm down areas of the brain that might be involved with depression. 00:03:01.495 --> 00:03:04.500 In 2005, this was a very experimental manipulation. 00:03:04.500 --> 00:03:08.895 This had previously only been done with lab rats and some types of monkeys. 00:03:08.895 --> 00:03:11.220 What they did, they wanted to test it on sick, 00:03:11.220 --> 00:03:13.420 severely depressed patients, which is 00:03:13.420 --> 00:03:16.020 what we often do with new medications or treatments. 00:03:16.020 --> 00:03:17.710 We pick those people who, 00:03:17.710 --> 00:03:20.040 for lack of a better term, have nothing to lose. 00:03:20.040 --> 00:03:22.250 They're at the bottom of the barrel. 00:03:22.250 --> 00:03:26.050 Really, they could use any type of possible treatment. 00:03:26.050 --> 00:03:30.560 Basically, beforehand, they took measures of the depression as using 00:03:30.560 --> 00:03:32.460 themselves as a comparison group to see if 00:03:32.460 --> 00:03:34.860 they get better over time with this new type of treatment. 00:03:34.860 --> 00:03:37.260 Then, of course, they undergo the surgery necessary to 00:03:37.260 --> 00:03:40.825 implant this deep brain stimulation device. 00:03:40.825 --> 00:03:45.760 Again, we're looking at individual changes in depression, not group-level changes. 00:03:45.760 --> 00:03:48.400 That's part of the single-case design. 00:03:48.400 --> 00:03:50.680 With some of the individuals, they found that it really 00:03:50.680 --> 00:03:53.835 made not much of a difference or no significant difference. 00:03:53.835 --> 00:03:56.100 Maybe they only went down a depression score, 00:03:56.100 --> 00:04:00.405 maybe from eight to seven on a one to ten depression score, 00:04:00.405 --> 00:04:04.020 whereas other people showed really dramatic decreases in depression, 00:04:04.020 --> 00:04:06.780 in some cases alleviating depression all the way. 00:04:06.780 --> 00:04:09.685 Again, we're looking at this in an individual basis. 00:04:09.685 --> 00:04:12.100 Each line represents a different person. 00:04:12.100 --> 00:04:14.870 In the end, the data looks something like this with 00:04:14.870 --> 00:04:19.590 basically two people showing negligible benefits or non-significant benefits, 00:04:19.590 --> 00:04:21.110 thankfully not getting any worse, 00:04:21.110 --> 00:04:26.790 but no real change and four of the six showing good benefits and in some cases, 00:04:26.790 --> 00:04:28.830 even complete alleviation from depression, 00:04:28.830 --> 00:04:30.855 which is, of course, what you'd want to see. 00:04:30.855 --> 00:04:34.380 Again, that's looking at an individual basis here. 00:04:34.380 --> 00:04:38.560 It's a quasi-experiment because there was no control group. 00:04:38.560 --> 00:04:41.200 A true control group in this case, 00:04:41.200 --> 00:04:43.990 and it would be unethical which is just why it wasn't done, 00:04:43.990 --> 00:04:48.700 would be to have people undergo surgery to implant this device, which is, of course, 00:04:48.700 --> 00:04:51.060 very risky, and then basically to 00:04:51.060 --> 00:04:54.495 think the device is on but to never actually turn it on. 00:04:54.495 --> 00:04:58.010 In this case, that's just too much to ask for a control group. 00:04:58.010 --> 00:05:01.320 Again, depression is a very detrimental thing. 00:05:01.320 --> 00:05:03.160 These are people who are severely depressed, 00:05:03.160 --> 00:05:06.400 so it would be unethical to withhold treatment from them. 00:05:06.400 --> 00:05:08.560 But then without this control group, 00:05:08.560 --> 00:05:10.360 there's lots of confounds that may have 00:05:10.360 --> 00:05:13.630 alleviated depression for these four out of the six individuals. 00:05:13.630 --> 00:05:16.300 The biggest one being a placebo effect. 00:05:16.300 --> 00:05:20.460 Lots and lots of studies show that when people think they're being treated, 00:05:20.460 --> 00:05:23.380 oftentimes, their symptoms will be lessened. 00:05:23.380 --> 00:05:30.510 This can be anything from an actual treatment to just a sugar pill or a placebo pill. 00:05:30.510 --> 00:05:32.440 Even with no treatment whatsoever, 00:05:32.440 --> 00:05:36.720 just the thought of being treated can oftentimes help people that mind over matter, 00:05:36.720 --> 00:05:38.480 especially with mental illness. 00:05:38.480 --> 00:05:40.840 If someone thinks they're being treated, they might think, well, 00:05:40.840 --> 00:05:43.080 I think I'm less depressed than I was before, 00:05:43.080 --> 00:05:45.675 but they're just thinking more optimistically. 00:05:45.675 --> 00:05:51.090 Another confound, and this is especially prevalent with research on the mentally 00:05:51.090 --> 00:05:52.810 ill is that lots of people with 00:05:52.810 --> 00:05:55.930 mental illness actually get over their mental illness on their own. 00:05:55.930 --> 00:05:59.110 This is something that we therapists don't talk about a lot because, of course, 00:05:59.110 --> 00:06:02.530 we like to tout that therapy and medication are really good things, which they are. 00:06:02.530 --> 00:06:07.090 They do help people oftentimes get over mental illness sooner than they would otherwise. 00:06:07.090 --> 00:06:09.230 But typically, about 60% of people with 00:06:09.230 --> 00:06:12.030 mental illness do get over it completely on their own. 00:06:12.030 --> 00:06:14.170 This includes anything from depression, 00:06:14.170 --> 00:06:16.830 usually not severe things like schizophrenia or bipolar, 00:06:16.830 --> 00:06:20.335 but depression, lots of mood disorders included. 00:06:20.335 --> 00:06:23.380 Now, this is unlikely in this group, 00:06:23.380 --> 00:06:25.680 though, especially at a 60% level, 00:06:25.680 --> 00:06:29.110 because they selected people with severe and prolonged depression, 00:06:29.110 --> 00:06:32.810 people who have had it for years, were previously untreatable. 00:06:32.810 --> 00:06:36.120 It is unlikely that these individuals would just snap out of 00:06:36.120 --> 00:06:40.640 it in the first initial weeks of this treatment. 00:06:42.260 --> 00:06:44.720 Again, I don't think this is such a problem in 00:06:44.720 --> 00:06:47.020 this study because these were very severe patients. 00:06:47.020 --> 00:06:50.920 But sometimes just getting a baseline measure of mental illness 00:06:50.920 --> 00:06:55.850 can help people motivate themselves to make changes in their life to get better. 00:06:55.850 --> 00:06:58.600 Especially for people with maybe mild to moderate depression, 00:06:58.600 --> 00:07:00.940 taking a depression inventory where they're listing 00:07:00.940 --> 00:07:03.940 all the things that's been wrong with them so obviously, 00:07:03.940 --> 00:07:05.760 depressed mood, maybe insomnia, 00:07:05.760 --> 00:07:09.120 not eating enough, isolation from friends and family. 00:07:09.120 --> 00:07:11.630 People might take that as a wake-up call and go, 00:07:11.630 --> 00:07:14.300 wow, I really need to eat more, 00:07:14.300 --> 00:07:15.840 and I need to rest more, 00:07:15.840 --> 00:07:18.200 and I need to contact my friends and family and actually 00:07:18.200 --> 00:07:21.040 can help them to snap themselves out of that depression. 00:07:21.040 --> 00:07:23.960 Again, I don't think this is a problem here because these were, 00:07:23.960 --> 00:07:26.990 again, very severely depressed patients. 00:07:26.990 --> 00:07:31.000 Probably is a case that this wouldn't play that big of a role. 00:07:31.250 --> 00:07:34.695 But one way to deal with these confounds, 00:07:34.695 --> 00:07:37.020 is to do what's called a reversal design. 00:07:37.020 --> 00:07:40.600 It's basically if you see an effect, which they did here, 00:07:40.600 --> 00:07:45.200 four out of six patients showed positive results, 00:07:45.200 --> 00:07:47.820 basically alleviations in their depression scores, 00:07:47.820 --> 00:07:49.380 then you might want to, 00:07:49.380 --> 00:07:51.500 in essence, take away the manipulation, 00:07:51.500 --> 00:07:54.620 take away the treatment, and see if they return back to their baseline scores, 00:07:54.620 --> 00:07:58.825 see if those four out of six return back to depressed scores. 00:07:58.825 --> 00:08:01.995 Now, this is called an ABA design. 00:08:01.995 --> 00:08:05.790 In this case, A really just means what's happening before their baseline and B, 00:08:05.790 --> 00:08:07.955 what happens after their treatment condition. 00:08:07.955 --> 00:08:10.710 ABA, going from baseline to treatment, 00:08:10.710 --> 00:08:14.405 and then hopefully back to baseline once you remove the treatment. 00:08:14.405 --> 00:08:17.565 They did this with one of the individuals. 00:08:17.565 --> 00:08:19.590 Whether or not this is ethical, 00:08:19.590 --> 00:08:22.810 this is a gray area, 00:08:22.810 --> 00:08:24.610 but at this point, this is one of the only ways to 00:08:24.610 --> 00:08:26.440 really rule out things like placebo effect. 00:08:26.440 --> 00:08:28.670 With one of the individuals who was showing 00:08:28.670 --> 00:08:32.090 a very positive result from the deep brain stimulation, they basically, 00:08:32.090 --> 00:08:34.550 because these people got a week-by-week checkup, 00:08:34.550 --> 00:08:38.670 where they fine-tuned the pacemaker inside them and all that, 00:08:38.670 --> 00:08:42.835 with this individual, they basically turned it off without telling him. 00:08:42.835 --> 00:08:45.130 Low and behold, within a couple of weeks, 00:08:45.130 --> 00:08:47.160 the patient returned back to baseline. 00:08:47.160 --> 00:08:49.470 This is a good indication 00:08:49.470 --> 00:08:53.050 that this is the actual treatment that's doing it and not just a placebo effect, 00:08:53.050 --> 00:08:54.230 because for all this person knows, 00:08:54.230 --> 00:08:55.600 they're still receiving treatment, 00:08:55.600 --> 00:08:58.510 so it rules out things like placebo effect, 00:08:58.510 --> 00:09:04.550 but also things like just self-recovery from depression. 00:09:04.700 --> 00:09:08.535 Of course, this is maybe unethical, 00:09:08.535 --> 00:09:11.730 because now you're withholding treatment for someone who really benefits from it. 00:09:11.730 --> 00:09:15.750 What most often they do with these types of designs is not just an ABA design, 00:09:15.750 --> 00:09:17.470 but an ABAB design. 00:09:17.470 --> 00:09:20.190 If they find that a person does return back to baseline, 00:09:20.190 --> 00:09:26.515 they again instill the treatment as soon as they start showing symptoms back to baseline. 00:09:26.515 --> 00:09:28.850 Hopefully, so that this individual doesn't 00:09:28.850 --> 00:09:31.605 have to suffer for any prolonged amount of time. 00:09:31.605 --> 00:09:33.750 In this case, again, they did this. 00:09:33.750 --> 00:09:36.700 They restarted the deep brain stimulation, 00:09:36.700 --> 00:09:38.220 again, without this person's knowledge, 00:09:38.220 --> 00:09:40.600 and within even a shorter period of time, 00:09:40.600 --> 00:09:44.415 a few days, he returned back to his treatment levels. 00:09:44.415 --> 00:09:48.690 This is even better for the whole anti-placebo argument because, 00:09:48.690 --> 00:09:49.880 again, this is without his knowledge. 00:09:49.880 --> 00:09:51.835 It's being turned on and off. 00:09:51.835 --> 00:09:57.230 This is a replication of the effect multiple times in the same individual. 00:09:57.230 --> 00:10:01.060 Really good indication that it really is the deep brain stimulation and not something 00:10:01.060 --> 00:10:03.460 else just random changes in the person 00:10:03.460 --> 00:10:07.120 over time or placebo effect causing this difference. 00:10:11.170 --> 00:10:14.710 [NOISE] Just some characteristics of the single-case design and 00:10:14.710 --> 00:10:17.725 a good way to differentiate it from regular types of experiments. 00:10:17.725 --> 00:10:19.270 For one, of course, 00:10:19.270 --> 00:10:21.830 it examines people individually as opposed to a group, 00:10:21.830 --> 00:10:24.110 so it's not going to talk about things like group averages. 00:10:24.110 --> 00:10:27.710 It's going to be saying more like four out of six people, for instance, 00:10:27.710 --> 00:10:31.925 in this case, did show significant improvement in their depression scores. 00:10:31.925 --> 00:10:35.025 Most of them do employ this reversal of design so 00:10:35.025 --> 00:10:38.280 either an ABA or an ABAB design. 00:10:38.280 --> 00:10:41.370 Of course, what makes it a quasi-experiment is, 00:10:41.370 --> 00:10:42.790 well, in this case, very clearly, 00:10:42.790 --> 00:10:44.310 there was no control group. 00:10:44.310 --> 00:10:47.050 Without a control group, you necessarily can't have 00:10:47.050 --> 00:10:50.970 experimental control or randomization because those require multiple groups. 00:10:50.970 --> 00:10:52.710 But even with multiple groups, 00:10:52.710 --> 00:10:54.150 usually with a quasi-experiment, 00:10:54.150 --> 00:10:57.450 you don't have any type of true control over 00:10:57.450 --> 00:11:01.590 what patients are experiencing other than the independent variable or the treatment, 00:11:01.590 --> 00:11:03.300 and there's no random assignment, 00:11:03.300 --> 00:11:07.115 because usually, you're dealing with person factors like depression. 00:11:07.115 --> 00:11:10.970 Most often these things are used to test the effectiveness of treatments. 00:11:10.970 --> 00:11:13.930 They're very common in therapeutic designs, 00:11:13.930 --> 00:11:17.030 especially involved with medications.