San Jose State University Inferential Statistics and Analytics Questions

1.

The first three class marks for a frequency distribution of “weights of college men” recorded to the nearest pound are 105, 115, and 125.
What is the class interval?

2.

The following frequency distribution shows the distribution of delivery times (in days) for swimstuff.com customer orders during the last month.

What is the relative frequency for orders delivered in less than three days?

3.

A sample of five full-service gasoline stations, each carrying three grades of gasoline, was taken, and the price per liter (to the nearest cent) was recorded for each grade of gasoline, as shown in the following table.

What is the median price of unleaded plus gas?

4.

The research director of a large oil company studied the buying habits of consumers with respect to the amount of gasoline purchased at full-service pumps. The sample mean amount is 11.5 gallons and the median amount is 11.95 gallons. The standard deviation of the sample is 4.5 gallons. What is Pearson’s coefficient of skewness here?

5.

A company set up a kiosk in the Mall of America for several hours and asked randomly selected people which color cell phone cover was their favorite. The results follow:

What is the probability that black, lime, or orange are the favorite colors, given that the person’s age is 21 or older?

6.

Elly’s Hotdog Emporium is famous for its chilidogs. Elly’s latest sales indicate that 30% of the customers order their chilidogs with hot peppers. Suppose 15 customers are selected at random. What is the probability that all 15 will want hot peppers?

7.

There are eight flights from Minneapolis to St. Cloud each day. The probability that any one flight is late is 0.10. Using the binomial probability formula, what is the probability that 1 or more are late?

8.

For each study below name the dependent variable, independent variable, and its levels.

• Thirty females were divided into three equal groups. One group was taught how to concentrate on their breathing. A second group was told to imagine that the day was very hot and that they would be allowed to place their hand in cool water. The third group was told nothing. All three groups placed their right hand in buckets of ice water for one minute. Afterward, they rated their pain on a scale of one to seven.
• During Rapid Eye Movement (REM) sleep, muscle tone is lost. For a rat sleeping on a 22-inch diameter platform over water, REM sleep is interrupted by falling into the water. With this technique you can deprive rats of REM sleep. Two groups of rats were deprived of REM sleep for zero or 72 hours. Afterward they learned to choose one arm of a T maze for food reinforcement. Each rat was given 30 trials in the T maze and its percentage of correct responses was calculated.
• Four groups of males were monitored during their sleep one night for the number of minutes of Rapid Eye Movement (REM). During the seven hours before sleep one group had seen six hours of TV, one had seen four hours, one had seen two hours, and one group had seen no TV.

9.

Describe what each of the following graphs is used for.

• line graph
• frequency polygon
• histogram
• bar graph

10.

Five “natural” athletes were asked to participate in a study of motor skills. As part of the study they learned to balance on a freestanding ladder (a skill that requires you to make quick, precise adjustments) and to perform the two-hand coordination task (an eye-hand coordination task). The scores are shown below.

Calculate a correlation coefficient and write a conclusion about motor skills in excellent athletes. Construct a scatterplot.

Initials Ladder Coordination

TH 8 1.7

IS 11 1.0

IS 3 1.2

TR 7 1.5

UE 9 0