Topic One: Statistical Analysis (Biology)

What are error bars used for?

To represent range, standard deviation, or other estimates of variability.

an overlap of error bars gives us what

a clue as to the significance of the results

what is a t-test

a statistical test which helps us determine the significance of the difference between the means of two populations

what does the mean not tell us

about the spread of the data

if t is less than cv,

accept h0

why do we reject h0 if t is greater than cv?

as the value of t increases, we become more confident that the results are real and not due to chance. If t is less than the critical value, we are less confident that the difference between the means is significant

what must the sample size do

be large enough to generate reliable data, and large enough to perform statistical tests

how do you calculate sample size

given amount - 2

what is the null hypothesis

h0 "there is no significant difference"

what does the t-test tell us (about probability)

it tells us the probability of two data sets being the same

what does a large overlap of error bars indicate

lots of shared data, results are not likely to be significantly different

what is the standard deviation

measure of the spread of most of the data

the higher value of p, the

more data overlap

what does no overlap of error bars indicate

no (or very little) shared data, results are likely to be significantly different

with the t-test we always start by saying the

null hypothesis

if t is greater than cv,

reject h0

what are two important things to consider when collecting large scale data

sample size and uncertainty/error of measurements

if p=1?

the data sets are exactly the same

if p=0?

the data sets are not at all the same

what is uncertainty

the margin of error in a measurement

if the t-test tells you to accept h0 then

the means are not significantly different

if the t-test tells you to reject h0 then

the means are significantly different

What is the definition of mean?

the measure of the central tendency of the data

the lower the value of p,

the more significant are our results

what is the definition of statistical analysis

the treatment of data collected in scientific investigations

what percent falls within one standard deviation of the mean

68%

how sure do we want to be on a t-test

95%

what percept falls within two standard deviations of the mean

95%

What are error bars?

Graphical representation of the variability of the data