Statistics 2: Null hypothesis Significance testing

what does probability vary between

0 (no possibility of event) and 1 (event will happen)

how to convert from % to probability

divide by 100

how to convert from probability to %

multiply by 100

research hypothesis

what we believe about the world

statistical hypothesis

 formal statements about population from which we are drawing our sample

Null hypothesis

formal statement that the effect we are looking for does not exist in the population

Alternative hypothesis

formal statement that the effect we are looking for does exist in the population

P value

• Probability of observing data at least as extreme as yours if the null hypothesis is true

• Provides an index of the (un)likeliness of data, under the assumption the null hypothesis is true

• If our data = very unlikely under the null hypothesis, P value = very small

cut off point P value

0.05

P value less than 0.05 (p<0.05)

result = statistically significant → REJECT NULL HYPOTHESIS

P value larger than 0.05 (p>0.05)

no statistically significant result → ACCEPT NULL HYPOTHESIS