Descriptive Statistics and Sampling

Question 1

What is a frequency table?

Answer 1

Question 2

What is QUANTitative data?

Answer 2

data with numeric values (e.g., height, income, age)

Question 3

What is a grouped frequency table?

Answer 3

groups data into classes (especially useful for continuous data)

Question 4

What is mean?

Answer 4

A math term for “average.” Mean is calculated by dividing the total by the number of values.

Question 5

What is continuous data?

Answer 5

Data that fill up a whole spectrum or range or values. Usually, these are measurements.

Examples: height, weight, distance, etc.

Question 6

What is discrete data?

Answer 6

Things that can only take specific values, typically countable values

For example: number of pets, shoe size

Question 7

What is QUALitative data?

Answer 7

Data can be separated into different categories that don’t have anything to do with numbers. (e.g., hair color, race, favorite artist)

Question 8

What are the 4 measures of variability?

Answer 8

• range(max-min)
• IQR (Q3-Q1) (interquartile range)
• standard deviation
• variance (standard deviation squared)

Question 9

What is a quartile?

Answer 9

Question 10

What are the three measures of central tendency?

Answer 10

• Mean (average)
• Median (middle #)
• Mode (most frequent #)

Question 11

What is a census

What are two disadvantages/advantages

Answer 11

A census is data collected by every member of the population

Two disadvantages for this is it is two expensive and it takes too long to collect all the information

Two advantages are every one in the population is used and it isn’t biased

Question 12

What is a sample

What are two disadvantages/advantages

Answer 12

A sample is a small amount of people from the population being used for the questionnaire

Two disadvantages of this are it doesn’t include everyone and it could be biased

Two advantages of this are it is quicker and cheaper

Question 13

What is the difference between population and sample?

Answer 13

Population is a group of people we want to know about (e.g., all American teenagers)

Sample is a subset of the population (useful because we usually can’t collect data on everyone) (e.g., 10 teenagers randomly selected from each of the 50 states, for a total sample of 500 teenagers)

Question 14

What is a mid-interval value?

Answer 14

the middle value in a class (useful when calculating descriptive statistics from a grouped frequency table)

Question 15

How do you calculate descriptive statistics of the data from a frequency table?

Answer 15

1. Enter the data (stat, enter)

If it is a normal frequency table, put the data values into L1 and the frequencies into L2.

If it is a grouped frequency table, put the mid-interval values of each class into L1 and the frequencies into L2.

2. Calculate descriptive statistics (stat, CALC, 1:1-Var Stats)

For FreqList, type in L2 (2nd, 2).

Question 16

What is the calculator symbol for mean?

Answer 16

x bar

Question 17

How do you calculate mean from a list of data?

Answer 17

Add all the values, divide by the number of numbers.

Question 18

What is the calculator symbol for standard deviation?

Answer 18

Question 19

How do you calculate the variance?

Answer 19

variance = standard deviation squared

Question 20

Simple Random Sample

Answer 20

Using a random number generator or other random method to randomly pick a subset of the population.

Asking the first fifty people you see is NOT random.

Question 21

Convenience sample

Answer 21

doing what is easy or convenient for the researcher

example: asking the first fifty people you see

downside: non-random, meaning that the sample is biased and not representative of the population.

Question 22

Quota sampling

Answer 22

Sampling people from one or more subgroups of your population using a nonrandom method.

For example: If you are surveying a school, you might want to get people from every grade, so you ask people you see after school to take your survey until you get ten people from each grade.

downside: non-random, meaning that the sample is biased and not representative of the population.

Question 23

systematic sampling

Answer 23

sampling every nth member of the population.

example: getting an alphabetical list of everyone in your school, then surveying every tenth person on your list.

Question 24

Stratified sampling

Answer 24

Randomly sampling from subgroups of your sample.

For example: If you are surveying a school, you might want to get people from every grade, so you use a random number generator to select ten people from every grade to take your survey.

Question 25

similarity and difference between stratified and quota sample

Answer 25

similarity: both have to do with subgroups

difference: stratified uses a random methodology to choose people to sample from the subgroups, while a quota sample is non-random.