The t-test for the difference between the means of two independent populations assumes that the respective:
a. sample sizes are equal. c. means are equal.
b. populations are normal. d. All of these choices are true.
Q. 2In exponentially smoothed time series, the smoothing constant w is chosen on the basis of how much smoothing is required. In general, a small value of w such as 0.1 results in very little smoothing, while a large value of w such as 0.8 results in too much smoothing.
Indicate whether the statement is true or false
Q. 3In constructing a confidence interval estimate for the difference between the means of two independent normally distributed populations, we:
a. pool the sample variances when the unknown population variances are equal.
b. pool the sample variances when the population variances are known and equal.
c. pool the sample variances when the population means are equal.
d. never pool the sample variances.
Q. 4The term seasonal variation may refer to the four traditional seasons, or to systematic patterns that occur during a month, a week, or even one day.
Indicate whether the statement is true or false
Q. 5In testing the difference between the means of two normal populations using two independent samples when the population variances are unequal, the sampling distribution of the resulting statistic is:
a. normal. c. approximately normal.
b. Student-t. d. approximately Student-t.
Q. 6To calculate the five-period moving average for a time series, we average the value in that time period, the values in the two preceding time periods, and the values in the two following time periods.
Indicate whether the statement is true or false
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