A social psychologist is interested in knowing whether people are more aggressive if they are in the presence of a weapon, such as a gun Treatment Condition- T1, as compared to when they are in a room with an innocuous item such as a tennis racket Control Condition-T2. The study used one sample of 17 college students and had all of the students in the sample participate in both treatment conditions. The mean of the difference scores was 18.0 and the variance (s2) was 612. An alpha level of .01 was set. Calculate the t. A  3.000 B  2.780 C  2.152 D  1.765

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 + ...