Y1 Stats C1-C3

Question 1

What is a population?

Answer 1

The whole set of items that are of interest.

Question 2

What is a census?

Answer 2

A measure that observes every member of the population.

Question 3

What is a sample?

Answer 3

A selection of observations taken from a subset of the population which is used to find out more about the population as a whole.

Question 4

What are the advantages of a census?

Answer 4

It is 100% accurate.

Question 5

What are the disadvantages of a census?

Answer 5

• They are time consuming and expensive
• It is hard to process that much data
• Can not be used when the testing process destroys the item

Question 6

What are the advantage of a sample?

Answer 6

• Less time consuming and cheaper than a census
• There is less data to process
• You don’t have to get everyone to respond

Question 7

What are the disadvantages of a sample?

Answer 7

• Data is less accurate

- It may not be large enough to give information about the sub groups in a population

Question 8

What is a sampling unit?

Answer 8

An individual unit of a population.

Question 9

What is a sampling frame?

Answer 9

A list of the sampling units.

Question 10

What is random sampling?

Answer 10

Sampling where every member has an equal chance of being selected.

Question 11

What are the types of random sampling?

Answer 11

• Simple random sampling
• Systematic sampling
• Stratified sampling

Question 12

What is simple random sampling?

Answer 12

When the sample units are chosen at random from the population.

Question 13

How can simple random sampling be done?

Answer 13

It can be done by lottery or by a random number generator.

Question 14

What is systematic sampling?

Answer 14

It is when all the members of the population are put in one list and every nth unit is selected.

Question 15

What is stratified sampling?

Answer 15

When a population is divided into “mutually exclusive strata” and a random sample is taken from each.

Question 16

What is the equation to calculate the number of sample units sampled in each strata?

Answer 16

Number in strata / number in population X overall sample size

Question 17

What are the advantages of simple random sampling?

Answer 17

• It is free of bias
• It is easy and cheap to implement on a small scale
• Every sample has an equal chance of being selected

Question 18

What are the disadvantages of simple random sampling?

Answer 18

• It requires a sampling frame

- It is not suitable for a large sample size

Question 19

What are the advantages of systematic sampling?

Answer 19

• It is simple and quick to use

- It is suitable for large populations and samples

Question 20

What are the disadvantages of systematic sampling?

Answer 20

• It needs a sampling frame

- It can introduce bias if the sampling frame is not randomly ordered

Question 21

What are the advantages of stratified sampling?

Answer 21

• It accurately reflects the population structure

- It guarantees proportional representations of sub groups

Question 22

What are the disadvantages of stratified sampling?

Answer 22

• The population must be separate-able into groups

- With each strata the same disadvantages of simple random are experienced

Question 23

What is quota sampling?

Answer 23

When the interviewer/researcher selects a sample that represents the characteristics of the whole population.

Question 24

What is opportunity sampling?

Answer 24

Taking a sample based on who is available at the time and wether or not they meet your criteria.

Question 25

What are the types of non-random sampling?

Answer 25

- Quota sampling | - Opportunity sampling

Question 26

What are the advantages of quota sampling?

Answer 26

- It allows a smaller sample to represent a large population - No sample frame needed - Quick, easy and inexpensive - It makes comparisons between groups easier

Question 27

What are the disadvantages of quota sampling?

Answer 27

- Biased - Can be inaccurate - Time and expense scales with the size of the population

Question 28

What are advantages of opportunity sampling?

Answer 28

- It’s easy to do | - It’s cheap

Question 29

What are the disadvantages of opportunity sampling?

Answer 29

- It is unlikely for the sample to be representative of the entire population - It is open to bias

Question 30

If data is coded with the formula y = (x-a)/b what is the mean of the coded data?

Answer 30

ybar =(xbar-a)/b

Question 31

If data is coded with the formula y = (x-a)/b what is the standard deviation of the coded data?

Answer 31

SDy = SDx/b (SD is a replacement for the standard deviation symbol)

Question 32

What is cleaning?

Answer 32

The process of removing anomalies from the data.

Question 33

What is the difference between an anomaly and an outlier?

Answer 33

An outlier is an extreme measurement that is well outside the normal range for that data. An anomaly is when an outlier is recorded due to incorrect data recording.