Statistics

Question 1

What is another name for normal distribution

Answer 1

Gaussian distribution curve

Question 2

What is another name for normal distribution

Answer 2

Gaussian distribution curve

Question 3

Why is normal distribution important

Answer 3

Followed by many biological variables
E.g bottom of curve it’s uncommon feature
Top of curve most common or average
End of curve less frequent but still common

Question 4

The mean is

Answer 4

Measure of location (average)

Question 5

Standard deviation is

Answer 5

Measure of dispersion (variability)

Question 6

Mean and standard deviation can be used to calculate what

Answer 6

Equation of the curve

Question 7

Why is calculating the equation of the curve useful

Answer 7

To calculate the population

Question 8

Subtracting one standard deviation from the mean and adding one standard deviation will be

Answer 8

68 percent of people will be within one standard deviation of the mean.

Question 9

Multiply standard deviation by 1.96 and add and subtract that from the mean.

Question 10

Predictions for normal distribution

Answer 10

50 percent of values lie below and above the

Question 11

95 percent of values lie between the mean Substrat 1.96x standard deviation

Answer 11

This means 95 percent of values between mean subtract 1.96xsd and mean add 1.96xsd.

Question 12

You only use the mean and standard deviation if the data is…

Answer 12

Normally distributed.

Question 13

Population

Answer 13

Entire group that we would ideally like to study

Question 14

Sample

Answer 14

Sub group of population we actually study

Question 15

Example
Population of interest;all men over 18 living in the uk
Sample: volunteer males aged over 20 working at factories in five cities in the uk
Is this representative

Answer 15

No

Question 16

Population value

Answer 16

Is the population mean
Example mean height of all men in the uk

Question 17

Sample value

Answer 17

Is sample mean
If sample is representative this is good unbiased estimate of the population mean

Question 18

Two main factors affect the size of this uncertainty

Answer 18

Sample size the more people we study the more confidence we have in estimates accuracy
Standard deviation (variability)

Question 19

Two related measures of uncertainty

Answer 19

Standard error- quantifies uncertainty of sample ,am as an estimate of the population mean
Confidence interval provides margin of error of sampl mean as estimate of the population mean.

Question 20

Standard error of mean

Answer 20

Smaller than sd of individual values

Question 21

What is confidence level

Answer 21

How sure we are that are results are accurate or not

Question 22

Standard error

Answer 22

Tells us how precise accurate our sample mean is as an estimate of the population mean.
Calculate by dividing the standard deviation by the square root of sample size
Used to calculate 95 percent confidence intervals expect 95 percent of sample means to fall within -+ 1.96SE of population mean.

Question 23

What can you calculate a confidence interval for
What statistics

Answer 23

Mean median risk proportion odds ratio

Question 24

How to calculate incidence risk

Answer 24

Developed disease/ total
Total= developed disease and did not develop it

Question 25

Null hypothesis definition

Answer 25

There is no real difference between groups

Question 26

Null hypothesis definition

Answer 26

There is no real difference between groups

Question 27

Conduct study and collect data
Perform a statistical test and calculate a test statistic
Convert test statistic into a p value
Interpret p value and draw conclusions

Question 28

Conduct study and collect data
Perform a statistical test and calculate a test statistic
Convert test statistic into a p value
Interpret p value and draw conclusions

Question 29

If p<0.05

Answer 29

Reject null hypothesis less than 5 percent probability of obtaining something

Question 30

What is the starting point of statistical analysis

Answer 30

Null hypothesis
Need to mention word ‘true’ or ‘in the population’

Question 31

Example: the true mean FEV1 for men is the same as the true mean FEV1 for women
Alternative hypothesis:the true mean fev1 for men is different to the true mean fev1 for women.

Answer 31

Take sample 39 men and 46 women
Observed difference in mean fev1 is 1.34 litres
Males mean 4.651 SD=0.761
Females mean=3.31 SD=0.657

Question 32

P less than 0.05 small
P>0.05 large

Question 33

If p is larger than 0.05

Answer 33

Not enough evidence to reject the null hypothesis at 5 percent significance

Question 34

T value

Answer 34

Mean difference/se of mean difference