Stats

Question 1

What is the equation for standard deviation

Answer 1

Question 2

What is the equation for outliers

Answer 2

Question 3

What is the equation to calculate skew

Answer 3

If Q2 - Q1 < Q3 - Q2, then positive skew

If Q2 - Q1 < Q3 - Q2, then negative skew

Question 4

What is the mean equal to in normal distribution

Answer 4

The mean, median and mode are all equal

Question 5

If pmcc is -ve, what do we do to CV to check significance

Answer 5

Make it negative and if CV is less than pmcc, then IS significant

Question 6

What are the 3 methods of random sampling

Answer 6

Simple random sampling
Systematic sampling
Stratified sampling

Question 7

What is simple random sampling

Answer 7

A simple random sample of size 𝑛 is one where every sample of size 𝑛 has an equal chance of being selected

Question 8

What is systematic sampling

Answer 8

A sample is formed by choosing members of a population at regular intervals using a list

Question 9

What is stratified sampling

Answer 9

Stratified sampling involves dividing the population into distinct subgroups, or strata, based on a specific characteristic (e.g., age, gender, income level). A random sample is then taken from each stratum in proportion to its size within the overall population. This method ensures that each subgroup is appropriately represented in the sample, enhancing the accuracy and representativeness of the results.

Question 10

What are the 2 types of non random sampling

Answer 10

Quota sampling
Opportunity sampling

Question 11

What is quota sampling

Answer 11

Where an interviewer or researcher selects a sample that reflects the characteristics of the whole population

Question 12

What is opportunity sampling

Answer 12

Taking the sample from people who are available at the time the study is carried out and who fit the criteria your looking for

Question 13

When coding data, what is the only action which alters standard deviation

Answer 13

Multiplying or dividing (and rooting/squaring)

Adding or subtracting doesn’t affect spread of data and so a standard deviation coded into y is = standard deviation in x if only coding is addition or subtraction

If we multiply or divide then rearrange the coding for x and apply whatever is applied to y in the code equation to the value of standard deviation obtained in y (only the division or addition)

Question 14

When doing hypothesis test with normal, which value do we use as H0 and which value do we test

Answer 14

H₀ value is the original assertion (whatever is believed)

The value we test is the value obtained from the sample

e.g. Mia believes the mean height of females in a country is less than 166cm
Sample is taken and mean found to be 164
Test her belief at 5%
H₀ = 166
P(H<164) = 0.03
0.03 < 0.05
Significant

Basically, it tells us how likely the observed value is, assuming the actual mean is true. If this likelihood is less than the significance level, then the result is unlikely — so we reject H₀, and the mean probably isn’t true