A researcher suspected that the number of betweenmeal snacks eaten by students in a day during final examinations might depend on the number of tests a student had to take on that day. The accompanying table shows joint probabilities, estimated from a survey. Number ofSnacks (Y)     Number of Tests (X) 0 1 2 3 0 1 2 3 0.07 0.07 0.06 0.02 0.09 0.06 0.07 0.04 0.06 0.07 0.14 0.16 0.01 0.01 0.03 0.04 a. Find the probability distribution of X and compute the mean number of tests taken by students on that day.b. Find the probability distribution of Y and, hence, the mean number of snacks eaten by students on that day.c. Find and interpret the conditional probability distribution of Y, given that X = 3.d. Find the covariance between X and Y.e. Are number of snacks and number of tests independent of each other?

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 + ...