week 7 SCM

Question 1

what is the sign test for?

Answer 1

• the sign test asks whether the proportion of positive differences between our hypothesised mean and our observed data mean is greater than would occur by chance
• we take the differences between each data point and the hypothesised mean value and compute whether they are positive or negative
• if the data is normally distributed and the actual mean is equal to the hypothesised mean, the proportion of hypothesised values above the mean(positive differences) should be 0.5

Question 2

what is the students t test formula to see if our actual mean is different from our hypothesised population mean?

Answer 2

T= actual mean - hypothesised population mean / SEM

it tests how large the deviation is compared to the variation in the sample means

Question 3

What is the Standard error mean formula?

Answer 3

standard distribution/ square root of number of samples

Question 4

what is the distribution of a t statistic under the null hypothesis

Answer 4

the t-distribution

Question 5

how could you visualise the difference between two means?

Answer 5

by using violin plots

Question 6

whats the students t test for the difference between two means include?

Answer 6

• the difference between means in the numerator

- the combined standard error in the denominators

Question 7

how do t tests work as a general linear model?

Answer 7

GLM : outcome = intercept (b0) + slope (b1) * IV + error

in t tests:
b1 is the difference in means between the two groups
b0 is the mean for the group that was coded as zero

• if you compute this in R as a general linear model it gives the same t statistic as a students t test

Question 8

what is the most commonly used effect size for comparison between two means?

Answer 8

Cohens D

Question 9

what is the formula for cohens D for a t test estimated using the general linear model

Answer 9

normal cohens D is D= difference between the means/SD residual

B1 is the difference between the means so B1 can be calculated as

D= B1/ SDresidual

Question 10

what does the t test linear model line look like

Answer 10

• the line of the t test liner model will be similar to the line between the two means of the violin plots

Question 11

how do you interpret cohens D output?

Answer 11

• 0-0.2 = negligible
• 0.2 - 0.5 = small
• 0.5-0.8 = medium
• 0.8+ = large

Question 12

what is a matrices?

Answer 12

• a rectangular array of numbers

Question 13

what are the entries of matrices called?

Answer 13

elements