Question

does stress affect the recall ability of police eyewitnesses? An experiment tested the eyewitness memory a week after nonstressful interview of a cooperative suspect. The memory of stressful interview of an uncooperative and belligerent suspect was also tested. The number of details recalled Nonstressed: n = 40 mean = 53.3 standard deviation = 11.6 Stressed: n = 40 mean = 45.3 standard deviation = 13.2 Is there enough evidence to indicate that the that nonstress suspect recalled more than the stressed suspect.

33. What test will you use? What is the name on the TI-83/84

34. State the null hypothesis (Ho).

35. State the alternative hypothesis (Ha).

36. What is the critical probability value (α)?

37. What is the P-value or P calculated?

38. Do you Reject null hypothesis or Fail to Reject null hypothesis

39. State your findings:

Answer 1

We need to perform a independent samples t-test for the following hypothesis:

Ho: u1 - u2 = 0
Ha: u1 - u2 > 0

u1 is the population mean for nonstress suspect
u2 is the popuation mean for stressed suspect

33. Press the STAT button on your calculator and highlight TESTS

Select the test: 2-SampTTest -> Highlight Stats -> Enter data (Highlight Pooled as "Yes" and ">u2")-> Highlight Calculate and hit ENTER

From the results,

36. Alpha = 0.05

37. p = 0.0026

38. As the p-value < 0.05, we can reject the null hypothesis.

39. Hence, we can conclude that we have strong evidence to say that the nonstress suspect recalled more than the stressed suspect.