Ackerman and Goldsmith (2011) found that students who studied text from printed hardcopy had better test scores than students who studied  text presented on the screen.  In a related study, a professor noticed that several students in a large class had purchased the e-book version of the course textbook.  For the final exam, the overall average for the entire class was μ= 81.7, but the  sample of n = 9 students who used e-books had a mean of M = 77.2 with ((SS =392) Is the sample sufficient to conclude that scores for students using e-books were sufficiently different from scores for the regular class? Use a two-tail test with α= .01.(not .05).

Definition Definition Measure of central tendency that is the average of a given data set. The mean value is evaluated as the quotient of the sum of all observations by the sample size. The mean, in contrast to a median, is affected by extreme values. Very large or very small values can distract the mean from the center of the data. Arithmetic mean: The most common type of mean is the arithmetic mean. It is evaluated using the formula: μ = 1 N ∑ i = 1 N x i Other types of means are the geometric mean, logarithmic mean, and harmonic mean. Geometric mean: The nth root of the product of n observations from a data set is defined as the geometric mean of the set: G = x 1 x 2 ... x n n Logarithmic mean: The difference of the natural logarithms of the two numbers, divided by the difference between the numbers is the logarithmic mean of the two numbers. The logarithmic mean is used particularly in heat transfer and mass transfer. ln x 2 − ln x 1 x 2 − x 1 Harmonic mean: The inverse of the arithmetic mean of the inverses of all the numbers in a data set is the harmonic mean of the data. 1 1 x 1 + 1 x 2 + ...