sample size

Sample Size

An important part of research design

calculation

Different study designs require different ____ methods; formulas differ for qualitative and quantitative variables

Effect size

Key Factors Sample Size (1)

Statistical power

Key Factors Sample Size (2)

Statistical test

Key Factors Sample Size (3)

Tolerance for errors in decision (Type 1 or Type 2 error)

Key Factors Sample Size (4)

Effect Size

Measures the size of an effect as it exists in the population, independent of experimental details like sample sizes

0.25

Small effect =

0.50

Medium effect =

0.80

Large effect =

Tolerance Error (Marginal Error)

Related to the researcher's confidence leveL

Alpha (α)

Often set at 5% or 0.05

Statistical Power

The likelihood that a study will detect an effect when there is an effect there to be detected.

beta (β)

Statistical power is inversely related to _____, the probability of making a Type II error.

Power = 1 – β

Statistical Power Formula

If statistical power is high, the probability of concluding there is no effect when there actually is one (Type II error) goes down.

Taro Yamane’s Formula

is used for determining sample size when working with a finite population and if the population size (N) is known.

G*Power software

is used for determining the sample size

G*Power software

It helps with computations involving the effect size, marginal error, statistical power, and the statistical test being used

Probability Sampling

These techniques use a "chance process" in selecting the sample.

Non-Probability Sampling

These techniques do not use a "chance process" in obtaining the sample.

random sample

is obtained from the population such that all samples of the same size have an equal likelihood of being selected

Systematic sampling

involves choosing a starting point by chance from a list of population members, and then selecting every nth element on the list

Stratified sampling

occurs when the population is divided into subpopulations, called strata, and a random sample is taken from each stratum.

homogeneous

in stratified sampling the population is first divided into _____ subgroups from which simple random samples are then drawn

cluster sample

is obtained by selecting some of the strata (or clusters) and then sampling from each of these.

cluster sample

It is also referred to as "area sampling" because the population is often spread out over a wide area.

Purposive sampling

is a non-probability sampling technique. The objects of the study has a unique characteristic, hence, not just anybody can be included as sample of the study.

criteria or requirements

Purposive sampling wherein the researcher sets __________ for who will be included as samples.

unique

Purposive sampling has objects of the study have ______ characteristics, meaning not just anybody can be included as a sample.

Convenience sampling

is a non-probability sampling technique. It simply utilizes results which are readily available.

Proportional and Equal

Types of stratified sampling include ________ Allocation and ____ Allocation.