Biostats - Lecture 12,13,14,15

Question 1

What is sampling

Answer 1

A smaller/more manageable version of a larger group
Containing the characteristics of the larger population

Question 2

What is wrong about sampling a WHOLE Population

Answer 2

It is costly and difficult to investigate an entire population

Question 3

Why do we have stastistcs in health science

Answer 3

Understand health of the population but not limited to

Question 4

Sample distribution of 30

Answer 4

More tight together

Question 5

Sampling distribution of 10

Answer 5

More spread out

Question 6

Categorical-variables

Answer 6

Type of data that may be divided into groups

Question 7

Continuous variables

Answer 7

A variable that can take an uncountable set of values or infinite set of values, eg: height, weight, age

Question 8

Standard diviation

Answer 8

• larger spread = larger STD
• it is a common method for measuring the amount of variation in a set of values, it tells us how far away each observation is from the mean or average
• a higher STD indicates greater variability in the dataset, while a lower STD indicates less variability

Question 9

How can errors occur

Answer 9

When there is too less of a sample or there is bias in a sample

Question 10

Population mean

Answer 10

The average value of the variable in the entire population

Question 11

Population SD

Answer 11

A measure of spread of the variable in the entire population

Question 12

Sample mean

Answer 12

The average value calculated from a sample population

Question 13

Sample SD

Answer 13

A measure of spread of the verable calculated from a sample population

Question 14

Sample distribution

Answer 14

Sample distrustion is centred on the population mean when there is no bias and the standard error is the SD of the sampling distribution, it measures the variability of sample means around the population mean

Question 15

Population proportion

Answer 15

The proportion of individuals or items in the entire population that possesses a particular characteristic or belonging to to a particular category

Question 16

Sample proportion

Answer 16

The proportion of individuals or items in a sample of the population that possesses a particular characteristic or belong to a particular category

Question 17

Populations with different variability so talking about the Population SD

Answer 17

as the population SD increases it gets more spread out

Question 18

Normal distribution

Answer 18

Symmetric bell curve

Question 19

What is in a normal distribution

Answer 19

95% will lie within 1.96 standard errors of the population mean

Question 20

Standard error

Answer 20

When the sample size is larger ( greater than 30 ) the sampling distribution tends to be a normal distribution. This is known as the CENTRAL LIMIT THEOREM
SE= S/ square root n

Question 21

95 confidence interval

Answer 21

General formula = plus minus 1.96 x SE

For means this becomes = mean (plus minus) 1.96 x s/ square root n

We also say : 95% confident that the true population mean lies bwteeen the lower and upper confidence interval

Question 22

Confidence intervals increasing sample size

Answer 22

Gets more squished together