Series forecasting for Business || Spring21 Time left 0:08:10 A random sample of 16 statistics examinations from a large population was taken. The average score in the sample was 78.6 and population variance was 64. We are interested in determining whether the average grade of the population is at least 75. Assume the distribution of the population of grades is normal. Then the critical value of the test at 5% level is O A. 1.753 OB. 1.96 OC. 1.645 d.p. None OE 1.645 NEXT PAGE IS PAGE

A new material will replace the old material only if there is significant evidence that the mean strength of the new material is more than 2 units higher than the mean strength of the old material.        Sample from new material:     mean  is  98.064   ,     SD  is   5.6     and sample size is 13 Sample from old material:       mean  is  95.282   ,     SD  is   5.8      and sample size is 78 We do not know population standard deviations. Consider the test           ?0:????−????=2H0:μnew−μold=2   vs.  ?0:????−????>2H0:μnew−μold>2  What is the p-value?       (Hint:  best to use software, or else the Desmos Calculator for the 2 sample T and Z test)  Give as a decimal between 0 and 1 accurate to at least 4 decimal places.

Sample data were collected in a study of calcium supplements and their effects on blood pressure. A placebo group and a calcium group began the study with measures of blood pressures for each group. What test would be most appropriate, if you have non-normal data? Name of Test _____________________________________________

A special bumper was installed on selected vehicles in a large fleet. The dollar cost of body repairs was recorded for all vehicles that were involved in accidents over a 1-year period. Those with the special bumper are the test group and the other vehicles are the control group, shown below. Each "repair incident" is defined as an invoice (which might include more than one separate type of damage).  Statistic Test Group Control Group Mean Damage x¯1x¯1 = $ 1,101 x¯2x¯2 = $ 1,766 Sample Standard Deviation s1 = $   696 s2 =   $ 838 Repair Incidents n1 =      12 n2 =       9  (a) Construct a 90 percent confidence interval for the true difference of the means assuming equal variances. (Round answers to 3 decimal places. Negative values should be indicated by a minus sign.) (b) Repeat part (a), using the assumption of unequal variances with Welch's formula for d.f. (Round answers to 2 decimal places. Negative values should be indicated by a minus sign.) (d) Construct separate…

A sample from a Normal population of n=6 observations yields an Xbar=100 and an s=20. What is the 90% CI for the mean?

When you take samples of size n - 100 from a normally distributed population, what will likely be the shape of the distribution of sample means? Right Skewed Left Skewed Normal