Nonpooled t-test: both normal and unequal population standard deviations (thus not the same shape)

Mann-Whitney: same shape but not normal.

Thus it is best to use the Mann-Whitney test (and it is also resistant to outliers).

Question

2021-07-01

Nonpooled t-test: both normal and unequal population standard deviations (thus not the same shape)

Mann-Whitney: same shape but not normal.

Thus it is best to use the Mann-Whitney test (and it is also resistant to outliers).

asked 2021-06-28

Suppose that you want to perform a hypothesis test to compare four population means, using independent samples. In each case, decide whether you would use the one-way ANOVA test, the Kruskal-Wallis test, or neither of these tests. Preliminary data analyses of the samples suggest that the four distributions of the variable a. are not normal but have the same shape. b. are normal and have the same shape.

asked 2021-06-04

Suppose that you want to perform a hypothesis test to compare several population means, using independent samples. In each case, decide whether you would use the one-way ANOVA test, the Kruskal-Wallis test, or neither of these tests. Preliminary data analyses of the samples suggest that the distributions of the variable are not normal and have quite different shapes.

asked 2020-12-24

asked 2021-05-25

The means of the number of revolutions per minute of two competing engines are to be compared. Thirty engines are randomly assigned to be tested. Both populations have normal distributions. Table 10.9 shows the result. Do the data indicate that Engine 2 has higher RPM than Engine 1? Test at a 5% level of significance. EngineSample Mean Number of RPMPopulation Standard Deviation 11,50050 21,60060 Table 10.9