Blog

Suppose that 20% of the Labrador Retrievers in the U.S. have a particular genetic defect.  We randomly select 7 Labs from the population consisting of all Labs in the U.S.  What is the probability that exactly 3 of the 7 dogs in this sample have the genetic defect?

A beef cattle nutritionist wants to compare the birth weights of calves from cows that receive two different diets during gestation.  He therefore selects 10 pairs of cows, where the cows within each pair have similar characteristics.  One cow within each pair is randomly assigned to diet 1, while the other cow in the pair is assigned to diet 2.  He obtains the following results: Mean difference in birth weights of the pairs of calves = 11 lb Standard deviation of the difference in birth weights of the pairs = 6.53 lb Which one of the following is the correct 95% confidence interval for the true mean difference in birth weights of the calves from cows receiving diet 1 vs. diet 2?

A local consumer reporter wants to compare the average costs of grocery items purchased at three different supermarkets – Kroger, Giant Eagle, and Meier.  Prices (in dollars) were recorded for a sample of 60 randomly selected grocery items at each of the three supermarkets.  In order to reduce item-to-item variation, the prices were recorded for each item on the same day at each supermarket. Item                          Kroger    Giant Eagle    Meier     1) Big Thirst Towel      $1.21       $1.49          $1.59 2) Post Golden Crisp    2.78         2.99            3.35 3) Tylenol Tablets         5.98         5.29            5.98           .                              .              .                   .           .                              .              .                   . 59) Colgate Shave       0.94         1.10            1.19 60) Kidney Beans        0.45          0.56            0.38                                                                                   Identify the experimental design employed for this experiment.

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 median grade of these 8 students.

The American Journal of Public Health published a study of the relationship between passive smoking and nasal allergies in Japanese female students.  The study revealed that 80% (i.e., p = 0.80) of the students from heavy-smoking families showed signs of nasal allergies on physical examinations.  Consider a sample of 10 Japanese female students exposed daily to heavy smoking in their families.  What is the probability that at least 7 (i.e., 7 or more) of the 10 students will have nasal allergies?

A study is conducted on a group of 9,000 high school students nationwide.  Each week for a period of 43 weeks participants must take an unannounced urine analysis to screen for illegal drug use.  What are the experimental units in this study?

The mean of the starting salary data that we have been using is 28,475 dollars and the standard deviation is 9,369 dollars.  According to the Empirical Rule, we expect 99% of the starting salaries to fall between what two numbers?

A swine producer reads a report stating that the average litter size in the US is 7.8 pigs per litter.  However, he feels that the average litter size on his farm is not 7.8 pigs/litter (he wants to detect departure in either direction from the hypothesized mean of 7.8 pigs/litter).  To test his hypothesis, he reviews his records for the past year and randomly selects 16 litters, which averaged 8.0 pigs/litter.  The standard deviation is 1 pig/litter. Use the appropriate table to find the critical value of the test statistic (use a significance level of α = 0.01).

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 point estimate.

You are interested in purchasing a new car.  One of the many points you wish to consider is the resale value of the car after 5 years of ownership.  Since you are particulary interested in a certain foreign sedan, you decide to estimate the resale value of this car with a 95% confidence interval.  You manage to obtain data on 16 recently resold 5-year-old foreign sedans of that model.  These 16 cars were resold at an average price of $10,000 with a standard deviation of $1,000. Estimate the true mean resale value of this model of foreign car using a 95% confidence interval.  What assumption must be met in order for this confidence interval to be valid?