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The grades of 8 students on an exam were as follows: Student Grade 1 66 2 70 3 64 4 88 5 74 6 72 7 87 8 79     Find the standard deviation of the grades of these 8 students.

Suppose that a 94% confidence interval for μ turns out to be (60 inches, 80 inches).  To make more useful inferences from the data, it is desired to reduce the width of the confidence interval.  What action should we take to reduce the width of the confidence interval?

Assume that a scientist conducts a 2 x 3 factorial experiment.  The Analysis of Variance table is shown below: Source          df          SS               MS               F     Total             17        1.73397 Factor A        1         0.10125       0.10125        23.0375 Factor B        2         0.81195       0.405975       92.3720 A x B             2         0.76803       0.384015       87.3754 Error            12        0.05274        0.004395                                                                                          Based on this analysis and a significance level of α = 0.05, what should the scientist conclude?

Breeders of the Longhorn breed of cattle select to increase the length of the horns (i.e., the distance from the tip of one horn to the tip of the other horn).  A Longhorn breeder would like to know the average length of horns found on Longhorn cattle in Texas.  A random sample of 144 Longhorn cattle yields a mean horn length of 72 inches and a standard deviation of 15 inches. Estimate the population mean for length of horns of Longhorn cattle in Texas using a 95% confidence interval.  What is the correct interpretation of the confidence interval that you derived?

We are interested in estimating the average driving time of students who commute to Ohio State.  How many students who commute need to be included in our sample to order to be 98% confident that the estimated mean driving time will be within 4 minutes of the true population mean driving time if the standard deviation of the driving times is 8 minutes?

Assume that we want to test the null hypothesis that the correlation between two variables is 0 vs. the alternative hypothesis that the correlation between these two variables is positive.  Based on a random sample of n = 20 observations, we calculate the sample correlation coefficient of r = 0.50.  Using a significance level of 0.05, which one of the following statements represents the correct conclusion?

Which one of the following is not a measure of variation?

Calculate the mean of the discrete probability distribution shown below:   X            2           4            5           10            P(X)       0.20       0.40       0.30       0.10  ____________________________________  

The  ∑  symbol in a statistical equation indicates that we are to perform which arithmetic operation?

Frame score in beef cattle is based on height at the hips and is used as a measure of skeletal size.  Frame scores range from 1 to 10 with a higher number indicating a taller animal.  Independent random samples of frame scores were selected from the Angus and Simmental breeds of beef cattle with the following results: Angus Simmental 5 7 6 7 7 8 5 6 7 7 6   Using the appropriate table, find the critical F value needed to test the null hypothesis that the breed means for frame score are equal (use α = 0.05).