maths skills Flashcards
what is Chi-squared?
a statistical test which tests the significance of the difference between observed and expected results
what are the overall steps to carrying out a Chi-squared test?
- write the null hypothesis
- create table with all the necessary information for the equation
- fill in table with necessary calculations
- use the equation to calculate the value for x^2
- calculate the degrees of freedom and find the corresponding critical value for p=0.05
- compare the x^2 value to the critical value and decide whether the difference is significant or not
- write the concluding statement
what do you say in the null hypothesis?
that there is no significant difference in the data and any difference is due to chance
how do you calculate the expected (E) value for each category?
add up all the observed values for the given categories and use the ratio to calculate what the expected would be for each one
what information do you need in your table to be able to apply it to the equation?
observed value for each category
expected value for each category
O-E
(O-E)^2
(O-E)^2/E
𝚺
what do you do to get 𝚺/the value for x^2?
calculate the value for (O-E)^2/E for each category and add them all together
how do you calculate the degrees of freedom?
number of categories - 1
how do you interpret the results of Chi-squared?
if x^2 is less than the critical value, accept the null hypothesis (no significant difference)
if x^2 is greater than the critical value, reject the null hypothesis (significant difference)
how do you structure the concluding statement?
the calculated value of _ is higher/lower than the critical value of _ for _ degrees of freedom at a significance level of 5%. therefore I can accept/reject the null hypothesis and conclude that _ as the probability that my results occurred by chance is greater/less than 5%.
