In: Statistics and Probability
To illustrate the effects of driving under the influence (DUI) of alcohol, a police officer brought a DUI simulator to a local high school. Student reaction time in an emergency was measured with unimpaired vision and also while wearing a pair of special goggles to simulate the effects of alcohol on vision. For a random sample of nine teenagers, the time (in seconds) required to bring the vehicle to a stop from a speed of 60 miles per hour was recorded. Complete parts (a) and (b). Note: A normal probability plot and boxplot of the data indicate that the differences are approximately normally distributed with no outliers. LOADING... Click the icon to view the data table. (a) Whether the student had unimpaired vision or wore goggles first was randomly selected. Why is this a good idea in designing the experiment? A. This is a good idea in designing the experiment because reaction times are different. B. This is a good idea in designing the experiment because the sample size is not large enough. C. This is a good idea in designing the experiment because it controls for any "learning" that may occur in using the simulator. Your answer is correct. (b) Use a 95% confidence interval to test if there is a difference in braking time with impaired vision and normal vision where the differences are computed as "impaired minus normal." The 95% confidence interval is ( nothing, nothing). (Round to the nearest thousandth as needed.)
Normal, Upper X Subscript i
4.49
4.34
4.58
4.56
4.31
4.83
4.55
5.00
4.79
Impaired, Upper Y Subscript i
5.86
5.85
5.51
5.29
5.90
5.49
5.23
5.63
5.63
Normal (X) Impaired (Y) d = X - Y
4.49 5.86 - 1.37
4.34 5.85 - 1.51
4.58 5.51 - 0.93
4.56 5.29 - 0.73
4.31 5.90 - 1.59
4.83 5.49 - 0.66
4.55 5.23 - 0.68
5.00 5.63 - 0.63
4.79 5.63 - 0.84
From the d values, the following statistics are calculated:
n = 9
= - 8.94/9 = - 0.9933
sd = 0.3878
SE = sd/
= 0.3878/ = 0.1293
ndf = 9 - 1 = 8
= 0.05
From Table, critical values of t = 2.3060
Confidence interval:
t SE
= - 0.9933 (2.3060 X 0.1293)
= - 0.9933 0.2981
= ( - 1.291, - 0.695)
So, the answer is:
The 95% confidence interval is (-1.291,-0.695)