Hypothesis Testing & P-Values Flashcards
what is the population
all individuals in which we are interested in
what is the sample
Group of individuals drawn from our population of interest, which we study in order to learn about the population
main aim of statistical analysis
is to use the information gained from a sample of individuals to make inferences about the population of interest.
There are two basic approaches to statistical analysis: Estimation (Confidence intervals) Hypothesis testing (P-values) .
what is the null hypothesis
where No difference (or change) will be observed between the measures and outcome
what are the hypothesis testing steps
set the null and alternative H Choose a sig level for the test carry out sig test obtain test stat compare test statistic to a distribution we expect it to follow if the null hypothesis is true obtain p-value make a decision
how do you work out the test stat
Observed value - Hypothesised value
/
Standard Error(of the observed value)
Compare this test statistic to a distribution we expect it to follow if the null hypothesis is true (e.g. Normal distribution) to obtain a P-value.
what do you use the p-value for
to make a decision about whether to reject, or not reject, your null hypothesis
if it is less than the sig level than the results are significnt
what does p-value mean
Probability of obtaining your results, or more extreme results, if the null hypothesis is true .
what is the range for a p-value
0-1
what does a small p-value mean
your results are unlikely when the null h is true
what does a large p-value mean
your results are likly when the null H is true
what is a type 1 error
false positive- rejected the null hypothesis, when it is fact true
chance of saying there is no difference, and you say there is
what is type 2 error
false negative- not rejected the null hypothesis, when in fact false
what is the Power of the study mean
The probability of rejecting the null hypothesis when it is actually false is called the POWER of the study (Power=1-β). It is the probability of concluding that there is a difference, when a difference truly exists.
what does a p-value of 0.001 mean
Your results are unlikely when the null hypothesis is true.
, and the results are stat sig, as the P-value is less than the sig level.
There is sufficent evidence to reject the null H and accept the alternative H.
what are some Misinterpretation of P values
A common misinterpretation of the P value is that it is:
the probability of the data having arisen by chance
or
the probability that the observed effect is not a real one.
does statistical significant mean Clinical Significance
Statistical significance does not necessarily mean the result is clinically significant/ practically important
How is Clinical Significance determined
through looking at the CI
what is the meaning if a CI includes 0
If the 95% CI does include zero then the hypothesis test will return a non-significant result.
what is the meaning if the CI dosen’t include 0
If the 95% CI does not include zero (or, more generally the value specified in the null hypothesis) then a hypothesis test will return a statistically significant result.
