Speed, size and strength are thought to be important factors in football performance. The paper “Physical and Performance Characteristics of NCAA Division I Football Players” (Research Quarterly for Exercise and Sport (1990): 395-401) reported on physical characteristics of Division I starting football players in the 1988 football season. Information for teams ranked in the top 30 was easily obtained, and it was reported that the mean weight of starters on top-30 teams was 110 kg. A sample of 23 starting players (various positions were represented) from Division I teams that were not ranked in the top 20 resulted in a sample mean of 103.3 kg and a sample standard deviation of 16.3 kg. Is there sufficient evidence to conclude that the mean weight for non-top-20 starters is less than the known value for top-20 teams? Conduct hypothesis test using α=.01

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 + ...