1) Identify the population and the sample and the variable of interest: The Gallup Organization contacts 1019 adult residents of the United States aged 18 or older and asks whether the events of September 11, 2001 were a life-altering experience.
a) Population:
b) Sample:
c) Variable of Interest:
2) Determine if the numerical value describes a parameter or a statistic:
a) The average price of a sample of 25 houses in a subdivision is $135,000.
b) The students in the Allen School have an average of 1.8 siblings.
c) A recent poll of 611 corporate executives showed that the average price of a corporate executive's car is $47,200.
d) The mean weight in ounces of all the ripe peaches in Virginia.
3) Determine whether each situation is an observational or experimental study:
a) A study comparing the effects of two different doses of an experimental drug on rats with cancer.
b) A study of whom likely voters plan to vote for in the upcoming election.
4) In each scenario, identify the sampling technique used for the study described.
a) In order to estimate the percentage of defects in a recent manufacturing batch, a quality control manager at Intel selects every 8th chip that comes off the assembly line.
b) A farmer divides his orchard into 50 subsections, randomly selects 4 and samples all the trees within the 4 subsections in order to approximate the yield of his orchard.
c) A survey regarding download time on a certain web site is administered on the internet by a market research firm to anyone who would like to take it.
d) A lobbyist for a major airspace firm contacts each legislator.
e) A school official divides the student population into five classes: freshman, sophomore. junior, senior, graduate student. The official takes a random sample from each class and asks the members' opinions regarding student services.
f) In an effort to identify whether an advertising campaign has been effective, a marketing firm conducts a nation-wide poll by randomly selecting individuals from a list of known users of the product.
5) The data below represent the percentage of divorces for selected countries.
68 56 43 38 24 15 65 55 43 35
21 15 64 53 41 34 19 13 63 52
41 28 18 13 63 49 40 26 18 12
Complete the extended frequency distribution below, using 6 classes.
6) Choose the best description of the shape of the distribution:
Approximately Symmetrical
Definitely Skewed to the Left
Definitely Skewed to the Right
Bimodal
7) A doctor randomly selects 30 of his 20-29-year-old patients and obtains the following data regarding their serum HDL cholesterol:
70 56 48 48 53 52 66 48 36 49
28 35 58 62 45 60 38 73 45 51
56 51 46 39 56 32 44 60 51 44
Draw up a Stem and Leaf Plot of the data.
8) Find the mean, median and mode (if one exists) for the following data:
2, 5, 4, 6, 7, 2, 4, 3
9) Sample annual salaries (in thousands of dollars) for public elementary school teachers are listed. Find the sample standard deviation. Round your answer to two decimal places. Use the chart provided if you need it.
23.3 19.9 27.8 25.3 41.3 19.3
10) A class of 25 students had the following ACT scores:
14, 16, 17, 18, 18, 18, 19, 19, 19, 20, 20, 21, 21, 23, 24, 24, 27, 27, 28, 29, 30, 31, 33, 33, 35.
Find the five-number summary and draw a boxplot that represents the data.
11) Find the area under the normal curve:
a) to the left of z = -1.47
b) to the right of z = -2.06
c) between z = -0.07 and z = 1.98
12) The weights of steers in a herd are distributed normally. The standard deviation is 150 lbs and the mean steer weight is 1200 lbs.
a) Find the probability that the weight of a randomly selected steer is less than 1136 lbs.
b) Find the probability that the weight of a randomly selected steer is greater than 1160 lbs.
c) Find the probability that the weight of a randomly selected steer is between 1300 and 1459 lbs.
13) A sample of size n = 80 is taken from a population with mean μ = 52 and standard deviation σ = 22.
a) Find the mean and standard deviation of the sampling distribution:
b) Find the probability that the sample mean x- is more than 51.
c) Find the probability that the sample mean x- is between 50 and 53.
14) Construct a histogram that represent the following height data.
| Height (in inches) |
| Class |
Frequency |
| 50-52 |
2 |
| 53-55 |
7 |
| 56-58 |
12 |
| 59-61 |
6 |
| 62-64 |
3 |