Statistics (2)

Question 1

Describe the characteristics of a normal distribution

Answer 1

Mean = Median = Mode
Symmetrical
68% values in 1SD and 95% in 2SD

Question 2

Name 2 reasons why data may not be normally distributed

Answer 2

1. Mean doesn’t equal median
2. 2SD below mean is impossible e.g height <0cm

Question 3

Name 3 examples of normal distribution

Answer 3

1. Height
2. Weight
3. Haemoglobin

Question 4

Name 3 examples of skewed distributions

Answer 4

1. Salaries
2. GCSEs passed
3. Marriages in a Year

Question 5

Describe the difference between parametric and non-parametric tests

Answer 5

Parametric assume data is normal so are more powerful whereas non-parametric make fewer assumptions so less powerful but may be used on non-normal or ordinal data

Question 6

What is a non-statistical hypothesis test?

Answer 6

Test deciding between null hypothesis and alternative hypothesis

Question 7

What is the function of a statistical hypothesis test?

Answer 7

Assess strength of evidence in data

Question 8

Describe 2 types of statistical hypothesis testing

Answer 8

1. One tailed shows direction
2. Two tailed doesn’t indicate direction

Question 9

Describe paired vs independent studies

Answer 9

• Individuals in comparison and sample group do not influence each other in independent studies
• In paired there are couplings between sample groups e.g data taken from same sample over time, twin studies etc.

Question 10

Describe the difference between statistical and clinical significance

Answer 10

May have statistical significance but not be clinically valuable e.g cost vs benefit

Question 11

What is the function of the p-value?

Answer 11

Tells us how likely the result of null hypothesis is to be true

Question 12

Describe convention for accepting p-value as significant

Answer 12

If p=small reject the null hypothesis for the alternative hypothesis, typically when p<0.05