Data was collected from CEOs of companies within both the low-tech industry and the consumer products industry. The following printout compares the mean return-to-pay ratios between CEOs in the low-tech industry with CEOs in the consumer products industry.
HYPOTHESIS: MEAN X = MEAN Y
SAMPLES SELECTED FROM RETURN
industry 1 | (low tech) | (NUMBER = 15) |
industry 3 | (consumer products) | (NUMBER = 15) |
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SAMPLE MEAN OF X = | 157 | .286 |
SAMPLE VARIANCE OF X = | 1563 | .45 |
SAMPLE MEAN OF Y = | 217 | .583 |
SAMPLE VARIANCE OF Y = | 1601 | .54 |
MEAN X - MEAN Y = | -60 | .2976 |
Using the printout, which of the following assumptions is not necessary for the test to be valid?
◦ The population means are equal.
◦ The population variances are equal.
◦ Both populations have approximately normal distributions.
◦ The samples were randomly and independently selected.