estimation

Question 1

definition of population

Answer 1

any collection of individuals in which we are interested

Question 2

definition of population distribution

Answer 2

frequency distribution of a variable in the population

Question 3

definition of population parameters

Answer 3

summary values calculated in populations

Question 4

definition of sample

Answer 4

subset of any population and is ideally selected to be representative of the population

Question 5

definition of random sample

Answer 5

drawn from a population in such a way that each member of the population has an equal chance of being selected

Question 6

what properties do we like our sample to have

Answer 6

accuracy/absence of bias-centred about to mean
precision/ repeatability-show little variation

Question 7

what is the sampling distribution of a statistic

Answer 7

frequency distribution of that statistic over all possible samples of a given size selected from the population

Question 8

what is the standard error

Answer 8

the std deviation of the sampling distribution of a statistic

Question 9

what is std error used to calculate

Answer 9

confidence intervals

Question 10

what is a confidence interval

Answer 10

a range of values centered on the sample estimate which is likely to include the population parameter with a given probability

Question 11

the equation for 95% CI for population mean

Answer 11

mean +- 1.96 s/sq root of n
(s / square root of n - std error of a mean)

Question 12

the equation for 95% CI for population proportion

Answer 12

mean +- 1.96 square root of p(1-p)/n

Question 13

definition of 95% confidence interval

Answer 13

in 95% of repeated samples from the population confidence intervals calculated in this way will capture the population parameter

Question 14

what are the 2 general properties of confidence intervals

Answer 14

1. the larger the sample size, the smaller the std error, the narrower the CI
2. higher the probability, wider the CI

Question 15

what doe we assume when calculating CI

Answer 15

the sampling distribution is normal

Question 16

changes required when using small sample

Answer 16

1) assume that variable of interest is normally distributed
2) no longer use normal distribution to obtain the multiplier - comes from t-test distribution

Question 17

equation of 95% CI in a small sample

Answer 17

mean +/- t(n-1,0.025) s/ square root of N
t has n-1 degrees of freedome