In: Statistics and Probability
Problem 3
You hypothesize that people who drive sports cars have faster reaction times than those who drive nonsports cars (e.g., sedans, pickup trucks, etc.). You design a task that measures response time to detect a visual target presented on a screen for 500 ms. The two types of drivers completed 300 trials of the task and the mean reaction times were calculated. The data are shown on the right. Did you find support for your hypothesis?
Use the four-step hypothesis testing procedure described in class, formatted as in the sample assignment. In addition, calculate 1) the effect size and 2) confidence interval associated with the data. Show your work.
Mean reaction times | |
sports car drivers | nonsports car drivers |
556 | 592 |
542 | 560 |
544 | 415 |
490 | 509 |
480 | 412 |
503 | 570 |
463 | 470 |
477 | 509 |
493 | 469 |
576 | 458 |
596 | 534 |
496 | 460 |
559 | 574 |
568 | 518 |
583 | 598 |
451 | 509 |
401 | 549 |
501 | 526 |
599 | 575 |
490 | 467 |
449 | 447 |
508 | 559 |
401 | 581 |
418 | 460 |
413 | 496 |
586 | 515 |
423 | 486 |
428 | 403 |
586 | 590 |
594 | 564 |
414 | 445 |
528 | 594 |
459 | 432 |
559 | 439 |
442 | 500 |
Two-Sample T-Test and CI: sports car drivers, nonsports car drivers
Method
μ₁: mean of sports car drivers |
µ₂: mean of nonsports car drivers |
Difference: μ₁ - µ₂ |
Equal variances are not assumed for this analysis.
Descriptive Statistics
Sample | N | Mean | StDev |
SE Mean |
sports car drivers | 35 | 502.2 | 64.0 | 11 |
nonsports car drivers | 35 | 508.1 | 58.9 | 10 |
Estimation for Difference
test statistic
confidence interval =
Difference |
95% Lower Bound for Difference |
-6.0 | -30.5 |
Test
Null hypothesis | H₀: μ₁ - µ₂ = 0 |
Alternative hypothesis | H₁: μ₁ - µ₂ > 0 |
T-Value | DF | P-Value |
-0.41 | 67 | 0.657 |
since p-value is greater than level of significance hence we fail to reject the null hypothesis and we conclude that there is significant evidence that people who drive sports cars have faster reaction times than those who drive nonsports cars.
cohens-d (effect size)
Cohen's d = (M2 - M1) ⁄ SDpooled
SDpooled = √((SD12 + SD22) ⁄ 2)
Cohen's d = (508.1 - 502.2) ⁄ 61.502886 = 0.09593.