1. A researcher conducts an experiment to investigate the...

1. A researcher conducts an experiment to investigate the effect of alcohol on the response time while driving. Subjects performed a response test before and after drinking a small amount of alcohol to observe its effect. Please identify the proper statistical method and compute the p-value. Subject ID | Before | After 1 | 4.4 | 5.6 2 | 3.2 | 4.6 3 | 3.6 | 4.0 4 | 4.2 | 5.5 5 | 6.4 | 6.5 6 | 3.3 | 5.5 7 | 3.9 | 4.7 8 | 4.7 | 3.5 9 | 2.5 | 3.0 10 | 5.6 | 5.0

Transcript

00:01 Okay, so because we're dealing with before and after data here, we need to make sure that these values stay paired together.

00:07 So the type of tests we want to run here is the paired t test or matched paired t test.

00:22 And the way we run this is first we have to find the differences between the values, and then we find the mean difference.

00:31 And then what we'll do is we'll run a t test after that.

00:35 So to find the differences, we're really just subtracting the before minus the after, and then we'll fill out the differences column.

00:44 So for instance, 4 .4 minus 5 .6 is going to give us negative 1 .2.

00:49 And we'll fill in the rest of the table similarly.

00:52 So we fill in the rest of the values again, subtracting before, minus, after, and we get the difference column filled in like that.

00:59 Now, what we want to do now is compute the mean difference.

01:03 And you can do that by hand or using a calculator.

01:06 I'm going to use technology because i also need the standard deviation of the difference, and it's just easier to do it with a calculator.

01:13 So we get a mean difference of negative 0 .61 and a standard deviation of one point, just one point out.

01:31 So those are our statistics for the differences.

01:37 And now what we're going to do is figure out the t score.

01:39 So it's going to be t is equal to the mean difference.

01:44 Minus the population difference, which we're going to assume that before and after are the same.

01:49 So that's just going to be zero...

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