After the data have already been collected and the supervisor has presented the

Question

After the data have already been collected and the supervisor has presented the above results to her boss, the supervisor's boss says that is would be absolutely disastrous if the bridge is kept open when it is actually unsafe (mu = 126). Without collecting additional data, but wanting to decrease the probability of such a disaster, the supervisor should: a. lower the p-value. b. raise the p-value. c. lower the alpha level. d. raise the alpha level. e. none of the above. Out of a random sample of 200 students at TAMU, 50 students reported drinking at least one glass of milk every day. To two decimal point accuracy, the value test statistic for testing whether the percentage of all TAMU students who drink at least one glass of milk every day is different from 30 percent is: a. -1.54. b. -2.97. c. -3.27. d. 1.54. e. none of the above. The word "pooled" in a "pooled estimate of variance" for a 2-sample t test refers to the fact that: a. there are two samples coming from populations with the same variance and a weighted average of the sample variances of both samples is used to estimate the common population variance. b. there are two samples used to compute the test statistic. c. the two samples used to compute the test statistic are not independent, so we have to pool data in the two samples. d. one needs to use t critical values rather than z critical values in forming rejection regions. e. none of the above.

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(16)

This is because lowering the alpha value increases the acceptance region and decreases the rejection region, so the chances of disaster are reduced.

(17)

Sample proportion, p = 50/200 = 0.25

Hypothesized proportion, p' = 0.30

t-statistic = (p-p')/( (p'*(1-p')) / n )0.5 = (0.25-0.30)/( (0.30*0.70) / 200 )0.5 = -1.54

(18)

This is because the concept of pooled variance is used for predicting variances of those distributions whose means may not be equal but have equal variances.

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