STT 231 EXAM 3A MSU QUESTIONS & ANSWERS
What is C.I. generally in the form of? - Answers :statistic ± MOE
The higher the confidence level... - Answers :the wider/bigger the confidence interval
(less precise range b/c bigger)
The larger the sample size... (for C.I.) - Answers :the narrower/smaller the confidence
interval becomes (more precise range b/c smaller)
C.I. should never be interpreted as a... - Answers :PROBABILITY
Ex: There is a 95% chance that the actual percent of coffee drinkers at MSU is between
75.6% and 90.4% (THIS IS WRONG)
When interpreting C.I. look for words like - Answers :"95% confident" or "if repeated..."
if 0 is between the C.I. then.... (about p-val) - Answers :the null CANNOT be rejected (p-
value will be greater than 0.05 because this means little evidence against the null
meaning we CANNOT reject it)
Effect size for mean - Answers :
Effect size for proportion - Answers :
2-sample inference for proportion conditions - Answers :(1) independent observations
(2) There must be at least 10 "success" and 10 "failure"observations expected in both
samples.
2-sample inference for mean conditions - Answers :(1) independent observations
(2) Populations should be normally distributed or both sample populations should be ≥
25
The distribution for the difference between 2 proportions is... - Answers :STANDARD
NORMAL DISTRIBUTION
The distribution for the difference between 2 means is... - Answers :T DISTRIBUTION
Symbol for chi-squared - Answers :χ2 (k)
What does k stand for in χ2 (k) - Answers :degrees of freedom
How do you calculate df (for chi-squared) - Answers :# of categories - 1
Chi-square is ALWAYS... - Answers :positive because it only explores the right side of a
curve (also always skewed right)
What is C.I. generally in the form of? - Answers :statistic ± MOE
The higher the confidence level... - Answers :the wider/bigger the confidence interval
(less precise range b/c bigger)
The larger the sample size... (for C.I.) - Answers :the narrower/smaller the confidence
interval becomes (more precise range b/c smaller)
C.I. should never be interpreted as a... - Answers :PROBABILITY
Ex: There is a 95% chance that the actual percent of coffee drinkers at MSU is between
75.6% and 90.4% (THIS IS WRONG)
When interpreting C.I. look for words like - Answers :"95% confident" or "if repeated..."
if 0 is between the C.I. then.... (about p-val) - Answers :the null CANNOT be rejected (p-
value will be greater than 0.05 because this means little evidence against the null
meaning we CANNOT reject it)
Effect size for mean - Answers :
Effect size for proportion - Answers :
2-sample inference for proportion conditions - Answers :(1) independent observations
(2) There must be at least 10 "success" and 10 "failure"observations expected in both
samples.
2-sample inference for mean conditions - Answers :(1) independent observations
(2) Populations should be normally distributed or both sample populations should be ≥
25
The distribution for the difference between 2 proportions is... - Answers :STANDARD
NORMAL DISTRIBUTION
The distribution for the difference between 2 means is... - Answers :T DISTRIBUTION
Symbol for chi-squared - Answers :χ2 (k)
What does k stand for in χ2 (k) - Answers :degrees of freedom
How do you calculate df (for chi-squared) - Answers :# of categories - 1
Chi-square is ALWAYS... - Answers :positive because it only explores the right side of a
curve (also always skewed right)
