Biostatistics

Question 1

What do we use representative samples for?

Answer 1

To make an inference about the population of interest. Because it is too costly and hard to investigate the entire population.

Question 2

How do you calculate %?

Answer 2

100 x number with characteristics / total number

Question 3

How do you calculate a proportion?

Answer 3

number with characteristic / total number

Question 4

How do you find the mean?

Answer 4

Sum of all values / total number of observations

Question 5

What is the mean?

Answer 5

Average value

Question 6

Define categorical variables

Answer 6

variables that can be categorised, cannot be in-between. must be one or the other.
e.g. eye colour

Question 7

Define continuous variables

Answer 7

Variables that are measurable, can take on any value.

e.g. height

Question 8

What graph is continuous variables best shown on?

Answer 8

Histogram
X-axis: value
Y-axis: percentage or number of the people I that range.

Question 9

What is the standard deviation?

Answer 9

The measure of the spread of data.

Question 10

What are 2 types of errors?

Answer 10

> Make our answers uncertain - unavoidable

> Moves our answers away from the truth -avoidable

Question 11

What is an example of uncertainty?

Answer 11

variability and is caused by taking a sample and measuring things imperfectly.

Question 12

How is bias avoided?

Answer 12

Taking a random sample from the whole population

Question 13

What are terminologies?

Answer 13

describe the centre and spread of the distributions.

Question 14

What is the relationship between SD and sample size?

Answer 14

The larger the sample size, the smaller the standard deviation, thus less variability.

Question 15

What distribution does sampling distribution follow?

Answer 15

Normal - bell symmetric bell-shaped curve

Question 16

What percentage of the sample mean lies within ±1.96 sd of the mean

Answer 16

95%

Question 17

What is the equation for the regression line?

Answer 17

y = a + b x X
y = what we trying to determine 
a = intercept 
b = slope 
x = variable

Question 18

What sample size determines if the distribution is normal and standard error can be calculated?

Answer 18

30

Question 19

How is the standard error calculated?

Answer 19

SE=s/√n

Question 20

What are the 95% confidence intervals used for?

Answer 20

If repeated sampling was carried out, 95% of the intervals would contain the true population mean.

Question 21

What is the relationship between sample size and confidence intervals?

Answer 21

As one increases the other becomes smaller

Question 22

The equation for confidence intervals

Answer 22

CI=Estimate±1.96×SE

Question 23

The equation for the means

Answer 23

x̄±1.96×s/√n

Question 24

What is the statement used for confidence intervals?

Answer 24

“We are 95% confidence that the true population mean lies between the lower and upper confidence limit”
OR
“our data support a true population mean that is between the lower and upper confidence limits”

Question 25

CI formula for proportions

Answer 25

Proportion±1.96×SE

Question 26

What does the 25th percentile represent in box plots?

Answer 26

25% of sample data is below and 75% above this point

Question 27

What does the median represent in box plots?

Answer 27

50% of sample data is below and 50% above this point

Question 28

What does the 75th percentile represent in box plots?

Answer 28

75% of sample data is below and 25% above this point