0:00:00.000,0:00:01.320 INSTRUCTOR: Single-case design. 0:00:01.320,0:00:05.380 This is probably one of the most common types of quasi-experimental designs, 0:00:05.380,0:00:08.980 and sometimes it gets a little confused with case studies for obvious reasons. 0:00:08.980,0:00:11.545 It includes single case design. 0:00:11.545,0:00:13.520 It sounds like a case study. 0:00:13.520,0:00:15.380 But unlike a case study, 0:00:15.380,0:00:17.980 so case studies usually just describe people. 0:00:17.980,0:00:23.090 There's no real manipulation or experiment going on, 0:00:23.090,0:00:25.820 there's no exposure to some type of stimulus, 0:00:25.820,0:00:27.430 and then to measure a reaction. 0:00:27.430,0:00:29.160 So with an actual case study, 0:00:29.160,0:00:30.860 you're just following them in their life, 0:00:30.860,0:00:33.460 seeing how they react normally to things, 0:00:33.460,0:00:36.450 and describing that very special case. 0:00:36.450,0:00:38.190 With a single-case design, 0:00:38.190,0:00:39.765 again, this is quasi-experimental, 0:00:39.765,0:00:43.515 you are looking at manipulating them in some way oftentimes. 0:00:43.515,0:00:47.265 How does someone with depression react to this type of therapy? 0:00:47.265,0:00:52.380 Or how does a pack-a-day smoker react to this type of medication or treatment? 0:00:52.380,0:00:56.790 Again, you are running a type of experiment, it's a quasi-experiment. 0:00:56.790,0:01:00.135 You're not just following these people around and recording their everyday lives, 0:01:00.135,0:01:02.340 you're trying to change them in some way, 0:01:02.340,0:01:06.255 usually, or treat them is maybe a better way of saying it. 0:01:06.255,0:01:10.740 Also, single case, and this is where I don't like the way this is named— 0:01:10.740,0:01:14.990 it's misleading—it implies that you're following one person. 0:01:14.990,0:01:19.000 That's really never the case with a single-case design. 0:01:19.000,0:01:22.330 The reason why we do call it a single-case design is because 0:01:22.330,0:01:26.190 we're usually analyzing data on an individual basis. 0:01:26.190,0:01:30.180 Pretty much all the analyses that we've been doing so far have been on group levels. 0:01:30.180,0:01:32.530 Comparing group averages, seeing if there's 0:01:32.530,0:01:35.595 a correlation between two variables on average. 0:01:35.595,0:01:38.300 The difference with a single-case design is you're 0:01:38.300,0:01:41.615 measuring change in individuals over time. 0:01:41.615,0:01:48.440 You often hear things like two out of three people benefited from this therapy. 0:01:48.440,0:01:52.025 Well, that's a quasi-experimental single-case statement. 0:01:52.025,0:01:54.320 You're measuring things on an individual basis. 0:01:54.320,0:01:57.020 You're not saying, on average, people got 30% better, 0:01:57.020,0:02:00.380 you're saying two out of three people got better. 0:02:01.610,0:02:05.095 I'm going to talk about one of the most common types of 0:02:05.095,0:02:09.745 single-case designs which involves some type of pre-post measure. 0:02:09.745,0:02:13.830 Usually, you're measuring the DV at a baseline. 0:02:13.830,0:02:15.860 I'll go and put this up at a baseline period. 0:02:15.860,0:02:18.530 We call that baseline because it's before manipulation, 0:02:18.530,0:02:20.040 it's just the regular level. 0:02:20.040,0:02:21.920 Then after the manipulation, 0:02:21.920,0:02:23.600 usually what we call a treatment period, 0:02:23.600,0:02:27.935 because some type of treatment or effect has been undertaken. 0:02:27.935,0:02:29.820 A real classic one, 0:02:29.820,0:02:31.650 one that's received a lot of interest lately as 0:02:31.650,0:02:36.210 a possible treatment for depression is called deep brain stimulation. 0:02:36.210,0:02:40.350 This is like having a pacemaker attached to your brain. 0:02:40.350,0:02:42.330 In a real way, it really is like that. 0:02:42.330,0:02:46.365 You have a pacemaker battery-like device implanted behind your collarbone, 0:02:46.365,0:02:49.630 and then electrodes go into very deep centers of your brain, 0:02:49.630,0:02:52.845 especially in the limbic system where depression is thought to originate. 0:02:52.845,0:02:57.040 These deep brain stimulations actually shut down 0:02:57.040,0:03:01.495 or calm down areas of the brain that might be involved with depression. 0:03:01.495,0:03:04.500 In 2005, this was a very experimental manipulation. 0:03:04.500,0:03:08.895 This had previously only been done with lab rats and some types of monkeys. 0:03:08.895,0:03:11.220 What they did, they wanted to test it on sick, 0:03:11.220,0:03:13.420 severely depressed patients, which is 0:03:13.420,0:03:16.020 what we often do with new medications or treatments. 0:03:16.020,0:03:17.710 We pick those people who, 0:03:17.710,0:03:20.040 for lack of a better term, have nothing to lose. 0:03:20.040,0:03:22.250 They're at the bottom of the barrel. 0:03:22.250,0:03:26.050 Really, they could use any type of possible treatment. 0:03:26.050,0:03:30.560 Basically, beforehand, they took measures of the depression as using 0:03:30.560,0:03:32.460 themselves as a comparison group to see if 0:03:32.460,0:03:34.860 they get better over time with this new type of treatment. 0:03:34.860,0:03:37.260 Then, of course, they undergo the surgery necessary to 0:03:37.260,0:03:40.825 implant this deep brain stimulation device. 0:03:40.825,0:03:45.760 Again, we're looking at individual changes in depression, not group-level changes. 0:03:45.760,0:03:48.400 That's part of the single-case design. 0:03:48.400,0:03:50.680 With some of the individuals, they found that it really 0:03:50.680,0:03:53.835 made not much of a difference or no significant difference. 0:03:53.835,0:03:56.100 Maybe they only went down a depression score, 0:03:56.100,0:04:00.405 maybe from eight to seven on a one to ten depression score, 0:04:00.405,0:04:04.020 whereas other people showed really dramatic decreases in depression, 0:04:04.020,0:04:06.780 in some cases alleviating depression all the way. 0:04:06.780,0:04:09.685 Again, we're looking at this in an individual basis. 0:04:09.685,0:04:12.100 Each line represents a different person. 0:04:12.100,0:04:14.870 In the end, the data looks something like this with 0:04:14.870,0:04:19.590 basically two people showing negligible benefits or non-significant benefits, 0:04:19.590,0:04:21.110 thankfully not getting any worse, 0:04:21.110,0:04:26.790 but no real change and four of the six showing good benefits and in some cases, 0:04:26.790,0:04:28.830 even complete alleviation from depression, 0:04:28.830,0:04:30.855 which is, of course, what you'd want to see. 0:04:30.855,0:04:34.380 Again, that's looking at an individual basis here. 0:04:34.380,0:04:38.560 It's a quasi-experiment because there was no control group. 0:04:38.560,0:04:41.200 A true control group in this case, 0:04:41.200,0:04:43.990 and it would be unethical which is just why it wasn't done, 0:04:43.990,0:04:48.700 would be to have people undergo surgery to implant this device, which is, of course, 0:04:48.700,0:04:51.060 very risky, and then basically to 0:04:51.060,0:04:54.495 think the device is on but to never actually turn it on. 0:04:54.495,0:04:58.010 In this case, that's just too much to ask for a control group. 0:04:58.010,0:05:01.320 Again, depression is a very detrimental thing. 0:05:01.320,0:05:03.160 These are people who are severely depressed, 0:05:03.160,0:05:06.400 so it would be unethical to withhold treatment from them. 0:05:06.400,0:05:08.560 But then without this control group, 0:05:08.560,0:05:10.360 there's lots of confounds that may have 0:05:10.360,0:05:13.630 alleviated depression for these four out of the six individuals. 0:05:13.630,0:05:16.300 The biggest one being a placebo effect. 0:05:16.300,0:05:20.460 Lots and lots of studies show that when people think they're being treated, 0:05:20.460,0:05:23.380 oftentimes, their symptoms will be lessened. 0:05:23.380,0:05:30.510 This can be anything from an actual treatment to just a sugar pill or a placebo pill. 0:05:30.510,0:05:32.440 Even with no treatment whatsoever, 0:05:32.440,0:05:36.720 just the thought of being treated can oftentimes help people that mind over matter, 0:05:36.720,0:05:38.480 especially with mental illness. 0:05:38.480,0:05:40.840 If someone thinks they're being treated, they might think, well, 0:05:40.840,0:05:43.080 I think I'm less depressed than I was before, 0:05:43.080,0:05:45.675 but they're just thinking more optimistically. 0:05:45.675,0:05:51.090 Another confound, and this is especially prevalent with research on the mentally 0:05:51.090,0:05:52.810 ill is that lots of people with 0:05:52.810,0:05:55.930 mental illness actually get over their mental illness on their own. 0:05:55.930,0:05:59.110 This is something that we therapists don't talk about a lot because, of course, 0:05:59.110,0:06:02.530 we like to tout that therapy and medication are really good things, which they are. 0:06:02.530,0:06:07.090 They do help people oftentimes get over mental illness sooner than they would otherwise. 0:06:07.090,0:06:09.230 But typically, about 60% of people with 0:06:09.230,0:06:12.030 mental illness do get over it completely on their own. 0:06:12.030,0:06:14.170 This includes anything from depression, 0:06:14.170,0:06:16.830 usually not severe things like schizophrenia or bipolar, 0:06:16.830,0:06:20.335 but depression, lots of mood disorders included. 0:06:20.335,0:06:23.380 Now, this is unlikely in this group, 0:06:23.380,0:06:25.680 though, especially at a 60% level, 0:06:25.680,0:06:29.110 because they selected people with severe and prolonged depression, 0:06:29.110,0:06:32.810 people who have had it for years, were previously untreatable. 0:06:32.810,0:06:36.120 It is unlikely that these individuals would just snap out of 0:06:36.120,0:06:40.640 it in the first initial weeks of this treatment. 0:06:42.260,0:06:44.720 Again, I don't think this is such a problem in 0:06:44.720,0:06:47.020 this study because these were very severe patients. 0:06:47.020,0:06:50.920 But sometimes just getting a baseline measure of mental illness 0:06:50.920,0:06:55.850 can help people motivate themselves to make changes in their life to get better. 0:06:55.850,0:06:58.600 Especially for people with maybe mild to moderate depression, 0:06:58.600,0:07:00.940 taking a depression inventory where they're listing 0:07:00.940,0:07:03.940 all the things that's been wrong with them so obviously, 0:07:03.940,0:07:05.760 depressed mood, maybe insomnia, 0:07:05.760,0:07:09.120 not eating enough, isolation from friends and family. 0:07:09.120,0:07:11.630 People might take that as a wake-up call and go, 0:07:11.630,0:07:14.300 wow, I really need to eat more, 0:07:14.300,0:07:15.840 and I need to rest more, 0:07:15.840,0:07:18.200 and I need to contact my friends and family and actually 0:07:18.200,0:07:21.040 can help them to snap themselves out of that depression. 0:07:21.040,0:07:23.960 Again, I don't think this is a problem here because these were, 0:07:23.960,0:07:26.990 again, very severely depressed patients. 0:07:26.990,0:07:31.000 Probably is a case that this wouldn't play that big of a role. 0:07:31.250,0:07:34.695 But one way to deal with these confounds, 0:07:34.695,0:07:37.020 is to do what's called a reversal design. 0:07:37.020,0:07:40.600 It's basically if you see an effect, which they did here, 0:07:40.600,0:07:45.200 four out of six patients showed positive results, 0:07:45.200,0:07:47.820 basically alleviations in their depression scores, 0:07:47.820,0:07:49.380 then you might want to, 0:07:49.380,0:07:51.500 in essence, take away the manipulation, 0:07:51.500,0:07:54.620 take away the treatment, and see if they return back to their baseline scores, 0:07:54.620,0:07:58.825 see if those four out of six return back to depressed scores. 0:07:58.825,0:08:01.995 Now, this is called an ABA design. 0:08:01.995,0:08:05.790 In this case, A really just means what's happening before their baseline and B, 0:08:05.790,0:08:07.955 what happens after their treatment condition. 0:08:07.955,0:08:10.710 ABA, going from baseline to treatment, 0:08:10.710,0:08:14.405 and then hopefully back to baseline once you remove the treatment. 0:08:14.405,0:08:17.565 They did this with one of the individuals. 0:08:17.565,0:08:19.590 Whether or not this is ethical, 0:08:19.590,0:08:22.810 this is a gray area, 0:08:22.810,0:08:24.610 but at this point, this is one of the only ways to 0:08:24.610,0:08:26.440 really rule out things like placebo effect. 0:08:26.440,0:08:28.670 With one of the individuals who was showing 0:08:28.670,0:08:32.090 a very positive result from the deep brain stimulation, they basically, 0:08:32.090,0:08:34.550 because these people got a week-by-week checkup, 0:08:34.550,0:08:38.670 where they fine-tuned the pacemaker inside them and all that, 0:08:38.670,0:08:42.835 with this individual, they basically turned it off without telling him. 0:08:42.835,0:08:45.130 Low and behold, within a couple of weeks, 0:08:45.130,0:08:47.160 the patient returned back to baseline. 0:08:47.160,0:08:49.470 This is a good indication 0:08:49.470,0:08:53.050 that this is the actual treatment that's doing it and not just a placebo effect, 0:08:53.050,0:08:54.230 because for all this person knows, 0:08:54.230,0:08:55.600 they're still receiving treatment, 0:08:55.600,0:08:58.510 so it rules out things like placebo effect, 0:08:58.510,0:09:04.550 but also things like just self-recovery from depression. 0:09:04.700,0:09:08.535 Of course, this is maybe unethical, 0:09:08.535,0:09:11.730 because now you're withholding treatment for someone who really benefits from it. 0:09:11.730,0:09:15.750 What most often they do with these types of designs is not just an ABA design, 0:09:15.750,0:09:17.470 but an ABAB design. 0:09:17.470,0:09:20.190 If they find that a person does return back to baseline, 0:09:20.190,0:09:26.515 they again instill the treatment as soon as they start showing symptoms back to baseline. 0:09:26.515,0:09:28.850 Hopefully, so that this individual doesn't 0:09:28.850,0:09:31.605 have to suffer for any prolonged amount of time. 0:09:31.605,0:09:33.750 In this case, again, they did this. 0:09:33.750,0:09:36.700 They restarted the deep brain stimulation, 0:09:36.700,0:09:38.220 again, without this person's knowledge, 0:09:38.220,0:09:40.600 and within even a shorter period of time, 0:09:40.600,0:09:44.415 a few days, he returned back to his treatment levels. 0:09:44.415,0:09:48.690 This is even better for the whole anti-placebo argument because, 0:09:48.690,0:09:49.880 again, this is without his knowledge. 0:09:49.880,0:09:51.835 It's being turned on and off. 0:09:51.835,0:09:57.230 This is a replication of the effect multiple times in the same individual. 0:09:57.230,0:10:01.060 Really good indication that it really is the deep brain stimulation and not something 0:10:01.060,0:10:03.460 else just random changes in the person 0:10:03.460,0:10:07.120 over time or placebo effect causing this difference. 0:10:11.170,0:10:14.710 [NOISE] Just some characteristics of the single-case design and 0:10:14.710,0:10:17.725 a good way to differentiate it from regular types of experiments. 0:10:17.725,0:10:19.270 For one, of course, 0:10:19.270,0:10:21.830 it examines people individually as opposed to a group, 0:10:21.830,0:10:24.110 so it's not going to talk about things like group averages. 0:10:24.110,0:10:27.710 It's going to be saying more like four out of six people, for instance, 0:10:27.710,0:10:31.925 in this case, did show significant improvement in their depression scores. 0:10:31.925,0:10:35.025 Most of them do employ this reversal of design so 0:10:35.025,0:10:38.280 either an ABA or an ABAB design. 0:10:38.280,0:10:41.370 Of course, what makes it a quasi-experiment is, 0:10:41.370,0:10:42.790 well, in this case, very clearly, 0:10:42.790,0:10:44.310 there was no control group. 0:10:44.310,0:10:47.050 Without a control group, you necessarily can't have 0:10:47.050,0:10:50.970 experimental control or randomization because those require multiple groups. 0:10:50.970,0:10:52.710 But even with multiple groups, 0:10:52.710,0:10:54.150 usually with a quasi-experiment, 0:10:54.150,0:10:57.450 you don't have any type of true control over 0:10:57.450,0:11:01.590 what patients are experiencing other than the independent variable or the treatment, 0:11:01.590,0:11:03.300 and there's no random assignment, 0:11:03.300,0:11:07.115 because usually, you're dealing with person factors like depression. 0:11:07.115,0:11:10.970 Most often these things are used to test the effectiveness of treatments. 0:11:10.970,0:11:13.930 They're very common in therapeutic designs, 0:11:13.930,0:11:17.030 especially involved with medications.