bias is measureable or nonmeasurable?

nonmeasurable

random error is measurable or nonmeasurable?

measurable

convenient sample is often a _______

bias sample

relationship of sample size to random error

larger sample size, smaller random error

considerations in sample

- is the sample representative of the population
- is the sample large enough
- are there other variables that explain the results

independent variable

presumed cause

dependent variable

outcome from the presumed cause

extraneous variables

must be kept constant

nominal scale

no order, only identifiers

ordinal scale

some order exists

scales of measurement

- nominal
- ordinal
- ratio
- interval

process of testing a statement about the population against an alternative statement

hypothesis testing

if p > a,

null hypothesis is not rejected

if p < a,

null hypothesis is rejected

two tailed hypothesis

null: mean is equal to X

alternative: mean is greater than or lesser than X

one tailed hypothesis

null: mean is greater than or equal to X

alternative: mean is less than X

the null and alternative hypotheses must be phrased such that they are:

mutually exclusive

collectively exhaustive

rejection of the null hypothesis means:

there is a clinically important difference

non-rejection of the null hypothesis:

there is no clinically important difference

type 1 error

concluding a difference when there is none

type 2 error

concluding the absence of a difference when there is a difference

what type of error is more serious

type 2

what type of estimate is preferable, point or confidence interval

confidence interval