stats reports

independent/explanatory variable

the variable that is not affected by other variables and is often changed in the investigation

dependent/response variable

the variable that changes as a result of the independent/explanatory variable being changed

causal claim

saying that the explanatory variable directly causes the response variable to change

conflict of interest

when a particular outcome would directly or indirectly benefit the researcher

bias

a systematic error that skews the result of a study, favouring certain outcomes over others

control group

a baseline group that does not receive the experimental treatment, used for comparison

randomisation

the process of assigning subjects to different groups purely by chance to reduce bias

replication

involves repeating the experiment multiple times to ensure that results are consistent and reliable

target population

the group of individuals you want to find information about

sample

includes some members of the target population

census

includes all members of the target population

sampling

when we take a small group from the population and use it to represent the entire population.

random sampling

where each bit of the population is numbered off and has an equal chance of

being selected.

cluster sampling

when you grab whole groups and use that as your sample

systematic sampling

where the parts of a population are ordered, and then every nth one is picked from a random starting point

stratified sampling

the population is split into subgroups of people with similar characteristics called ‘strata’, samples of people are taken from each strata in proportion to the number that the population

sampling errors

these occur as a result of the sampling process, because the variability between samples can never be completely avoided

non sampling errors

these result from the way information is collected from the sample

survey

a method of data collection where a set of questions is used to gather information from a group of people

polls

a method of data collection that focuses on collecting information about people’s opinions or preferences

sample size

the number of observations or data points collected in a survey or experiment

replication

conducting the same experiment again under the same conditions

margin of error rule of thumb

1/√n

margin of error formula

z√px(1-p)/n

95% CI z value

1.96

99% CI z value

2.576

margin of error

a measure of the range within which the true value of a population is expected to fall

confidence interval

indicates the percentage of times the true population parameter lies within the confidence interval in repeated sampling

confidence interval formula

p ± margin of error

correlation

a relationship between two variables, so that when one chnages, the other also changes

causation

when one variable is changed this causes a change in another variable

confounding variables

outside factors that affect the study results and aren’t controlled