Question

In: Statistics and Probability

Problem 3 You hypothesize that people who drive sports cars have faster reaction times than those...

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

Solutions

Expert Solution

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.


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