For a certain nationwide standardized test there are two commonly used preparation products on the market: StudyFocus and Prepara. A researcher in the Education department at a nearby university wants to determine if there is any difference between the two products on the mean score on the test by their users.

The researcher obtains the scores on the test from a random sample of 16 users of StudyFocus and a random sample of 14 users of Prepara. (These samples are chosen independently.) For the users of StudyFocus, their sample mean is 482.1 with a sample variance of 4623. For the users of Prepara, their sample mean is 503.4 with a sample variance of 788.6.

Assume that the two populations of scores are approximately normally distributed. Can the researcher conclude, at the 0.05

level of significance, that there is a difference between the population mean of the scores on the test by the users of StudyFocus and the population mean of the scores on the test by the users of Prepara?

Perform a two-tailed test. Carry your intermediate computations to three or more decimal places.

Question:

What is the degrees of freedom?