AS Stats

Question 1

How do you work out the interquartile range?

Answer 1

Upper quartile (halfway between middle and end) - Lower quartile (halfway between start and middle)

Question 2

What are the 3 different patterns a set of data could form?

Answer 2

• Symmetrical
• Positive skew
• Negative skew.

Question 3

What does bi-variate mean?

Answer 3

2 variables.

Question 4

How do you work out if a value is an outlier?

Answer 4

Upper: UQ + 1.5 x IQR

Lower: LQ - 1.5 x IQR

If the value is above the upper outlier value or below the lower one then it is an outlier.

Question 5

What is H0?

Answer 5

The null hypothesis.

Question 6

What is H1?

Answer 6

The alternative hypothesis.

Question 7

When do we accept H0?

Answer 7

When the answer is > significance level.

Question 8

When do we reject H0?

Answer 8

If the answer is < significance level.

Question 9

What does each letter represent in X ~ B (n, p)?

Answer 9

• n = number of trials
• p = probability of success
• Ignore X and B.

Question 10

How do you find the critical region?

Answer 10

Find the values of X where the probability > significance level.

Question 11

What does P(X=r) = altogether?

Answer 11

1

Question 12

What do r and X represent in P(X=r)?

Answer 12

• r = list of possible values
• X = actual outcome.

Question 13

What are the 7 types of sampling?

Answer 13

• Opportunity sample
• Simple random sample
• Systematic sample
• Self-selected sample
• Stratified sample
• Cluster sample
• Quota sample.

Question 14

What is the sampling frame?

Answer 14

A list of the population.

Question 15

What is an opportunity sample?

Answer 15

• Taking samples from people who are available at the time and fit the criteria
• Easy in terms of time and money
• Can produce a biased sample due to the researcher choosing people from own social and cultural group
• Participants may decline and it becomes self-selected
• No sampling frame.

Question 16

What is a simple random sample?

Answer 16

• Every member of the population has an equal chance of being chosen
• Involves choosing at random the samples, e.g. drawing tickets out of a box
• Isn’t always possible since you may not have a list of everyone in the population.

Question 17

What is a systematic sample?

Answer 17

• Involves choosing individuals to form a sample
• For example, if the parent population was all year 11 students in a school, you would get an alphabetic list and choose every 10th one.

Question 18

What is a self-selected sample?

Answer 18

• Individuals in the sample have chosen to be in it
• For example if someone responds to an advert to be included in the sample
• People volunteer
• Quick
• Not representative.

Question 19

What is a stratified sample?

Answer 19

• If the parent population can be divided into subgroups, or strata, then stratified sampling ensures all strata are sampled
• If numbers sampled from each strata are proportional to the sizes of the strata, then this is proportional stratified sampling.

Question 20

What is a cluster sample?

Answer 20

• If the population can be and is divided into subgroups representative of the population, a sample can be taken from one of these subgroups
• For example divided into towns or countries.

Question 21

What is a quota sample?

Answer 21

• Similar to a stratified sample, but is specified in terms of the number of data items required within each stratum
• This is often used by interviewers, where the selection of samples is up to them
• Asking them if they meet the criteria.

Question 22

When would a 2-tailed hypothesis test occur?

Answer 22

If the probability of an event has changed - it could have increased or decreased, so it is a 2-tailed test.

Question 23

How would a 2-tailed hypothesis test be different?

Answer 23

• p would be not equal to, as opposed to greater or less than
• You have to divide the sig level by 2 as it is 2-tailed.