Blog

A sales representative for a seedcorn company tells his boss that within the past year he has contacted 80% of the farmers in his sales district.  However, his boss makes random phone calls to 36 farmers in the sales district and finds that the sales rep only contacted 24 of them in the past year. Based on the hypothesis test, what should the boss conclude?  Explain.

In seeking a free agent NFL running back, a general manager is looking for a player with a high mean for yards gained per carry and a small standard deviation.  Suppose the GM wishes to compare the mean yards gained per carry for two free agents based on independent random samples of their yards gained per carry.  Data from last year’s pro football season indicate that σ1 and σ2 are both equal to approximately 5 yards.  If the GM wants to estimate the difference in means for yards gained per carry by the two running backs correct to within 1 yard with a confidence level of 0.90, how many carries would have to be observed for each of the two players?  Assume equal sample sizes.

We randomly select 100,000 samples of size n from a population.  We calculate the sample mean (X-bar) for each of the 100,000 random samples and graph the relative frequency distribution for these 100,000 values of X-bar.  This relative frequency distribution is called the ____________________ of X-bar.

The variable measured in an experiment (e.g., weights of dogs, litter sizes of rabbits, etc.) is called the ____________.

The weights (in pounds) of 17 pigs are used to construct the following stem-and-leaf display (the first two digits were used as the stem and the last digit was used as the leaf): Stem                   Leaf                                       16          0     5 17          — 18          — 19          — 20          — 21          — 22          2     4     6 23          0     9 24          0     1     2     3     4     5     9 25          3 26          — 27          — 28          0     5   Based on this stem-and-leaf display, the median weight is __________ lb.

The body weight in pounds (variable X) and fleece weight in pounds (variable Y) of a random sample of four ewes are as follows: Body weight, lb (X)            Fleece weight, lb (Y)           140                                            9           145                                          10           155                                          10           160                                          12                                                                                      Derive the equation for the regression line.  What would be the predicted fleece weight of a ewe that weighs 152 lb?

A farmer weighs his calves on the day they are weaned.  The weight of the lightest calf is 300 lb and the weight of the heaviest calf is 650 lb.  Based on this information, which measure of variation could be calculated?

Suppose a 99% confidence interval for the population mean for weight of cows of a certain breed turns out to be (800 lb, 1400 lb).  To make more useful inferences from the data, it is desired to reduce the width of the confidence interval.  Which of the following will result in a reduced width of the confidence interval?

Assume that the mean length of time required to complete the Columbus Marathon was 4.5 hours and that the standard deviation of the times was 0.50 hours.  Assume that the racing times were approximately normally distributed.  Only 10% of the runners would be expected to complete the race in less than x hours.  Find the value of x.

The Central Limit Theorem is important in statistics, because: