Exam 8: Parameter Estimates

For the following set of sample scores, find the estimated standard error of the mean: 12, 11, 9, 4, 8, 2.

For the following set of sample scores, estimate the population mean within a .95 confidence interval: 3, 6, 5, 3, 3, 7, 7, 5, 6. 112

Other things being equal, the higher the value of the t ratio

A single-sample t ratio is only considered to be significant when

The only t ratios which can possibly lead to a reject of the null hypothesis are those which are positive in sign.

When there is a failure to reject Ho, one must conclude that the difference between the sample mean and the population mean is probably not due to chance.

A researcher is interested in evaluating a certain brand of radial auto tire. Twenty tires are randomly selected from retail outlets throughout the country, and each is placed on a special machine which rotates the tires at a constant speed (equivalent to 55 miles per hour) against the friction equivalent of a 4000 pound auto being driven on a smooth highway. Each tire is run until there is no tread left. The number of miles (in thousands) were as follows: 40, 30, 32, 35, 39, 35, 31, 36, 37, 35, 34, 35, 37, 34, 36, 38, 35, 36, 35, 36. -Setting alpha at .05, test the hypothesis that this sample of tires could represent a population whose mean was 36.50

With extremely large sample sizes, the difference in values between the estimated population standard deviation and the true standard deviation of the sample become minimal.

Whenever Ho is rejected, then