Statistical tests

Question 1

why do we use stats tests

Answer 1

determine whether or not a set of data differs significantly and if the outcomes were produced by chance

Question 2

what is the null hypothesis

Answer 2

a statement which states that there will be no significant correlation or difference between the variables you’re investigating

Question 3

what happens to the null hypothesis at the end of the stat test

Answer 3

you either accept or reject the null hypothesis depending on the result

Question 4

what does significant correlation/difference mean

Answer 4

unlikely to have occurred due to chance

Question 5

accepting or rejecting null hypothesis comes down to …

Answer 5

probability and chance

Question 6

what value determines the probability of the correlation/ difference

Answer 6

probability value or P value

Question 7

in biology the minimum p value is….

Answer 7

0.05 (5%)

Question 8

when do we use student t-test

Answer 8

comparing 2 means of the same variable to see if there is a statistical difference

Question 9

when do we use the chi-squared test

Answer 9

collecting data about no. of individuals in particular categories

Question 10

when do we use the correlation coefficient (spearman’s rank)

Answer 10

looking for a correlation between DIFFERENT variables (see if there is a significant correlation)

Question 11

the null hypothesis allows it to be…..

Answer 11

an unbiased position/view

Question 12

how would you make a null hypothesis for the t-test

Answer 12

there is no significant difference between X1 and X2

Question 13

how would you make a null hypothesis for correlation coefficient

Answer 13

there is no significant correlation between X and Y

Question 14

where does the test statistic come from?

Answer 14

from using the equations specific to each test

Question 15

what must I do with the test statistic

Answer 15

compare with the critical value from the table (degrees of freedom and p value)

Question 16

how do you get the degrees of freedom in t-test

Answer 16

no. of values in variable 1 minus 1, then adding the no. of values in variable 2 minus 1
(n1 - 1) + (n2 - 1)

Question 17

how do you get the degrees of freedom in a chi-squared test

Answer 17

no. of categories minus 1

Question 18

when looking for test statistic which p value do we go to?

Answer 18

0.05 (5%)

Question 19

how do you get the degrees of freedom in a correlation coefficient test

Answer 19

no. of pairs of groups

Question 20

if test statistic is less than critical value….

Answer 20

accept the null hypothesis, no significant difference, there is more than a 0.05 probability that difference is due to chance

Question 21

if the test statistic is greater than the critical value…

Answer 21

reject the null hypothesis, is a significant difference, there is less than a 0.05 probability that the difference is due to chance

Question 22

the closer you get to -1 in spearman’s rank there is a stronger….

Answer 22

negative correlation

Question 23

the closer you get to 1 in spearman’s rank there is a stronger…

Answer 23

positive correlation

Question 24

how do you find the expected frequency in a chi-squared test?

Answer 24

add together the observed frequencies. Then divide that number by how many observed frequencies. i.e. 34+ 66 = 100 100/2 = 50 (expected frequency)