lecture 6 - ANOVA: multiple groups

Question 1

statistical methods for dealing with multiple comparisons usually have two steps which are:

Answer 1

1. an overall test
2. a detailed follow up analysis

Question 2

this test regarding analysis of variance is used to see if there is good evidence that any of the parameters differs from its hypothesized value

Answer 2

overall test

Question 3

this test regarding analysis of variance is used to decided which of the parameters differs from their hypothesized value and to estimate the size of the difference

Answer 3

detailed follow-up analysis

Question 4

_______ assesses mean differences by comparing the variability explained by different sources. what matters is not how far apart the sample means are, but how far apart they are relative to the variability of individual observations

Answer 4

ANOVA

Question 5

true/false: in ANOVA we are concerned with variability within each group and variability between the groups

Answer 5

true

Question 6

if the analysis of variance shows the difference of the means within and between the groups is approximately 1, does that mean there is treatment effect or no treatment effect

Answer 6

no treatment effect

Question 7

if the analysis of variance shows the difference of the means within and between the groups is greater than 1, does that mean there is treatment effect or no treatment effect

Answer 7

treatment effect

Question 8

what describes this formula?
(variance between sample means)/(variance amount individuals within each sample)

same as MSB/MSW

Answer 8

F statistic

Question 9

what are some assumptions for ANOVA

Answer 9

• random samples
• independence
• indépendant observation within each sample
• normal population
• homogeneity variance

Question 10

an assumption of ANOVA: simple random samples eliminate bias

Answer 10

random samples

Question 11

an assumption of ANOVA: critical assumption. we have independent samples, one from each of k populations. For dependant measures (repeated measures on the subject) a repeated measures ANOVA model is available

Answer 11

independence

Question 12

an assumption of ANOVA: the population from which the simple random samples are drawn must be normally distributed. ANOVA is somewhat robust to this assumption for larger samples

Answer 12

normal population

Question 13

an assumption of ANOVA: the σ2 for each population must be equal (even when the group means are different). there is no simple rule of assessing this, as a rule of thumb the F test will be approximately correct when the largest sample s2 is no more than twice as large as the smallest sample

Answer 13

homogeneity of variance

Question 14

what is the hypothesis in ANOVA (one-way model)

Answer 14

H0 = μ1 = μ2 =…….= μk (the means are all the same)

Question 15

______ (MSW/MSB) always works

Answer 15

MSW - mean squares within

Question 16

_______ (MSW/MSB) only work if H0 is true

Answer 16

MSB - mean squares between

Question 17

what is the next step once the F statistic is calculated?

Answer 17

we find the critical value for the F statistic from the table

Question 18

when is the null hypothesis rejected based on the calculated and critical F statistic

Answer 18

reject null hypothesis if F > F critical