Biostatistics

Question 1

What is a categorical variable?

Answer 1

Investigates categories e.g. gender, eye colour, ethnicity
Summarise using proportions or percentages

Question 2

What is a continuous variable?

Answer 2

• Numerical variable e.g. height, weight, age
• Displayed as an average such as a mean

Question 3

What are the two types of error?

Answer 3

Variability : Makes answers more uncertain
Bias : Makes answer further from truth

Question 4

What factors can affect standard error?

Answer 4

• Sample size: greater sample size, closer sample mean will be to population mean = small standard error, narrow distribution. Highly variable sample means large standard error, wide distribution
• Population variability: more variability less likely sample will be to population mean = more spread out, distribution wider, greater standard error

Question 5

Normal Distribution

Answer 5

• Bell shaped curve
• 95% of sample falls within 1.96 standard errors of population mean
• Only when more than 30 in a sample

Question 6

Confidence intervals and standard error equation

Answer 6

CI= +/- 1.96 x SE
(SE is standard error)

SE= s/sqrt n
(s is standard deviation, n is sample size)

Question 7

What is a significant difference when comparing samples?

Answer 7

If the resultant sample mean is over 1.96 standard error away from mean then there is a significant difference