iv, dv, ev and types of experiments
What is meant by an independent variable (IV)?
The variable manipulated by the researcher to see its effect on the dependent variable
What is meant by random sampling?
Every member of the target population has an equal chance of being selected, e.g., names drawn from a hat.
What is meant by an independent groups design?
Different participants take part in each condition of the experiment. Their results are then compared between groups.
What is meant by the mean?
It is the arithmetic average, calculated by adding all the scores together and dividing by the number of scores.
What is a directional hypothesis?
A prediction that states the specific direction of the relationship or difference
Identify the dependent variable (DV) in this study:
A researcher tests whether sleep affects exam performance
Exam performance (e.g., score on the test)
Give one strength of opportunity sampling.
It is quick and convenient because participants are chosen based on availability.
Give one strength of a repeated measures design
Participant variables are controlled because the same people take part in all conditions.
State one strength of using the median.
It is not affected by extreme values (outliers).
What is a non-directional hypothesis?
A prediction that states there will be a difference or relationship, but does not say in which direction
What is an extraneous variable (EV)? Give one example
A variable other than the IV that could affect the DV if not controlled, e.g., noise in the room
What is a weakness of volunteer sampling?
Participants are more likely to be motivated or helpful, so the sample may be biased.
What is meant by a matched pairs design?
Participants are matched on key variables (e.g., age, IQ) and then split so that each group has similar individuals.
What is the mode?
The most frequently occurring score in a data set.
What is meant by a null hypothesis?
A prediction that there will be no significant difference or relationship, and any result is due to chance
What is meant by a laboratory experiment?
An experiment carried out in a controlled setting where the IV is manipulated and EVs are controlled.
What is meant by stratified sampling?
The population is divided into subgroups (strata) and participants are randomly selected in proportion to their occurrence in the population
State one weakness of using an independent groups design
Participant variables (e.g., differences in ability) may affect results.
What is meant by the range?
A measure of dispersion calculated by subtracting the lowest score from the highest score.
What is meant by correlation in psychology?
A statistical test that measures the strength and direction of the relationship between two co-variables
Give one strength of a field experiment
High ecological validity because behaviour occurs in a natural environment.
Give one strength of systematic sampling.
It is unbiased once the starting point is chosen, as participants are selected at regular intervals.
Why might a researcher choose a repeated measures design instead of an independent groups design?
Fewer participants are needed and differences between conditions are less likely to be due to participant variables.
Give one weakness of using the standard deviation
It is harder to calculate and understand compared to the range
Give one strength of using a correlation.
It allows researchers to study relationships between variables without manipulation