# Sampling Techniques

**Topics:**Random variable, Probability theory, Normal distribution

**Pages:**25 (5470 words)

**Published:**August 3, 2011

For each description of sampling, decide if the sampling technique is

A.Simple Random

B.Stratified

C.Cluster

D.Systematic

E.Convenience

1.In order to estimate the percentage of defects in a recent manufacturing batch, a quality control manager at Intel selected every 8th chip that comes off the assembly line starting with the 3rd, until she obtains a sample of 140 chips.

2.In order to determine the average IQ of ninth-grade students, a school psychologist obtains a list of all high schools in the local public school system. She randomly selects five of these schools and administers an IQ test to all ninth-grade students at the selected schools.

3.In an effort to determine customer satisfaction, United Airlines randomly selects 50 flights during a certain week and surveys all passengers on the flights.

4.A member of Congress wishes to determine her constituency’s opinion regarding estate taxes. She divides her constituency into three income classes: low-income households, middle-income households, and upper-income households. She then takes a random sample of households from each income class.

5.In an effort to identify whether an advertising campaign has been effective, a marketing firm conducts a nationwide poll by randomly selecting individuals form a list of known users of the product.

6.A radio station asks its listeners to call in their opinion regarding the use of American forces in peacekeeping missions.

7.A farmer divides his orchards into 50 subsections, randomly selects 4 and samples all of the trees within the 4 subsections in order to approximate the yield of his orchard.

8.A school official divides the student population into five classes: freshman, sophomore, junior, senior and graduate student. The official takes random sample from each class and asks the members’ opinions regarding student services.

9.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.

10.A lobby has a list of 100 senators of the United States. In order to determine the Senate’s position regarding farm subsidies, they decide to talk to every seventh senator on the list starting with the third.

Chapter 1 – Frequency Table construction

The following table shows the number of arrivals at a Wendy’s restaurant during several 15-minute intervals.

76664

566114

27124

65537

22975

62657

68265

46985

Define the variable. X =

Construct a Frequency table of the above data. Make sure you title each column and fill in each space.

Answer the following questions using your frequency table.

1. What does the relative frequency column add to? Why is this so?

2. RF(X = 5)

2. RF(X > 5) =

3. RF(X < 5) =

4. RF(3 < X < 7) =

Chapter 2 – Boxplot

For each of the following sets of data

a. construct a boxplot

b. state which quarter has the largest spread and what that spread is c. state which quarter has the smallest spread and what that spread is d. find the IQR

e. determine if there are any outliers by identifying them

1. This data is a list of three-year rates of return of 40 small-capitalization growth mutual funds. 27.416.710.824.125.9

12.728.522.218.417.4

22.629.611.645.916.6

32.147.710.918.423.3

18.23225.523.738.1

23.714.712.831.121.9

18.421.32719.615.8

14.73719.218.529.1

2. This data is a list of the percent of persons living in poverty in each of the 50 US states in 1997.

14.89.41310.411.216.323.415.214.112.5

8.510.113.316.410.710.016.611.715.110.5

18.89.111.618.49.79.611.811.416.717.5

18.414.38.210.718.67.712.311.98.38.5

16.814.79.69.310.69.211.813.110.912.7

3. The following table gives the number of...

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