Question
Most individuals are aware of the fact that the average annual repair cost for an automobile depends on the age of the automobile. A researcher
Most individuals are aware of the fact that the average annual repair cost for an automobile depends on the age of the automobile. A researcher is interested in finding out whether the variance of the annual repair costs also increases with the age of the automobile. A sample of 26 automobiles 4 years old showed a sample standard deviation for annual repair costs of $171.18 and a sample of 23 automobiles 2 years old showed a sample standard deviation for annual repair costs of $118.75. Let 4 year old automobiles be represented by population 1. The data is located in the Microsoft Excel Online file below.
Car Age and Repair Cost ($) | F-Test Two-Sample for Variances | ||||
4 years | 2 years | ||||
788 | 637 | 4 years | 2 years | ||
839 | 431 | Mean | 784.6154 | 450.7826 | |
778 | 454 | Variance | 29301.93 | 14101.54 | |
791 | 404 | Observations | 26 | 23 | |
889 | 410 | df | 25 | 22 | |
791 | 713 | F | 2.077924 | ||
775 | 573 | P(F<=f) one-tail | 0.043639 | ||
943 | 469 | F Critical one-tail | 2.019644 | ||
1013 | 155 | ||||
943 | 419 | ||||
1060 | 399 | Significance Level (alpha) | 0.05 | ||
405 | 524 | ||||
955 | 396 | Test Statistic (2 decimals) | 2.08 | ||
874 | 548 | ||||
886 | 396 | Critical Value (2 decimals) | 2.02 | ||
336 | 598 | ||||
733 | 391 | p-value (4 decimals) | 0.0436 | ||
654 | 336 | ||||
507 | 370 | Reject the null hypothesis? | Yes | ||
823 | 455 | ||||
708 | 356 | ||||
808 | 365 | ||||
898 | 569 | ||||
790 | |||||
801 | |||||
612 |
State the null and alternative versions of the research hypothesis that the variance in annual repair costs is larger for the older automobiles.
H 0 : 21
H a : 21
2. Conduct the hypothesis test at a 0.01 level of significance.
Calculate the value of the test statistic (2 decimals).
2.08
Calculate the critical value (2 decimals).
2.02 <------- This is flagging as incorrect even inputting the formula given.
Calculate the p-value (4 decimals).
0.0436
Reject null hypothesis? No
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