In: Statistics and Probability
Suppose the National Transportation Safety Board (NTSB) wants to examine the safety of compact cars, midsize cars, and full-size cars. It collects a sample of ten for each of the treatments (cars types). Using the hypothetical data provided below, test whether the mean pressure applied to the driver’s head during a crash test is equal for each types of car. At the 0.05 significance level, can we conclude that there is a difference in the mean pressures between compact, midsize or full size cars.) (Enter all numeric values in 4 decimals unless otherwise noted.)
| Compact | Midsize | Fullsize |
| 300 | 404 | 499 |
| 354 | 443 | 426 |
| 234 | 421 | 329 |
| 399 | 418 | 421 |
| 278 | 499 | 426 |
| 358 | 374 | 414 |
| 379 | 362 | 332 |
| 356 | 305 | 360 |
| 196 | 375 | 394 |
| 156 | 438 | 537 |
Collect the sample data and calculate the value of the test statistic
Test statistic:_______
p-value: is 0.00157
Calculate the 95% Tukey simultaneous confidence intervals. (4 decimals)
____≤μ_c-μ_m≤_____
_____≤μ_c-μ_f≤_____
_____≤μ_m-μ_f≤_____
87.7289 ≤μ_c-μ_m≤ 64.5289
97.8289≤μ_c-μ_f≤54.4289
86.2289≤μ_m-μ_f≤66.0289
Below are the calculations,
| Tukey-Kramer Multiple Comparisons | Fromules | |
| Mean Group 1 | 124.65 | |
| n Group 1 | 10 | |
| Mean Group 2 | 113.05 | |
| n Group 2 | 10 | |
| Mean Group 3 | 102.95 | |
| n Group 3 | 10 | |
| MSW | 0.9211 | |
| Q Statistic | 3.77 | |
| Comparison of Group 1 to Group 2 | ||
| Absolute Difference | 11.6 | ABS(B3-B5) |
| Standard Error of Difference | 0.303496293 | SQRT((B9/2)*((1/B4)+(1/B6))) |
| Critical Range | 1.144181025 | B10*B13 |
| Means of Groups 1 and 2 are | Different | IF(B12>B14,"Different","Not Different") |
| Comparison of Group 1 to Group 3 | ||
| Absolute Difference | 21.7 | |
| Standard Error of Difference | 0.303496293 | |
| Critical Range | 1.144181025 | |
| Means of Groups 1 and 3 are | Different | |
| Comparison of Group 2 to Group 3 | ||
| Absolute Difference | 10.1 | |
| Standard Error of Difference | 0.303496293 | |
| Critical Range | 1.144181025 | |
| Means of Groups 2 and 3 are | Different | |
| Group 1 vs Group 2: Diff=-11.6000, 95%CI=-87.7289 to 64.5289, p=0.9246 | ||
| Group 1 vs Group 3: Diff=-21.7000, 95%CI=-97.8289 to 54.4289, p=0.7616 | ||
| Group 2 vs Group 3: Diff=-10.1000, 95%CI=-86.2289 to 66.0289, p=0.9422 | ||