Experiments Flashcards
What is the independent variable?
The part of the experiment that is different for each group of participants
What is the dependant variable?
What you are measuring as a result of the independent variable
What are the controls?
Parts of the study that are the same for everyone
What is the experimental condition?
The group of participants who experience the manipulation of the independent variable.
What is the control condition?
The group of participants who do not experience the manipulation of the independent variable.
What is the aim?
The aim of an experiment is to establish cause and effect. This means we want to find out what effect the IV has on the DV.
What is a laboratory experiment?
An experiment that takes place in a controlled setting
What is a field experiment?
An experiment that takes place in a naturalistic setting
What is a quasi experiment?
An experiment with an IV that is not manipulated by the researcher
(e.g age or race)
What are the strengths of laboratory experiments?
- Controlled settings reduce the effects of extraneous variables (high construct validity)
- Increases internal reliability as has high level of controls
What are the weaknesses of laboratory experiments?
- Low ecological validity (so cannot generalise findings to real life)
- More effort to conduct
- People may act weird in a controlled setting (lowering construct validity)
What are the strengths of field experiments?
- High ecological validity as takes place in a natural setting
- High construct validity (participants may be more at ease due to the natural environment)
- Less effort to conduct
What are the weaknesses of field experiments?
- Higher chance of extraneous variables influencing the results (lowering construct validity)
- Participants may have different experiences, therefore lowering internal reliability
What are the strengths of quasi experiments?
- High ecological validity as the IV is not manipulated
- Helps us study variables we cannot manipulate
What are the weaknesses of quasi experiments?
- Difficult to conduct
- Cannot control some participant variables that may influence results (lowering construct validity)
What are extraneous variables?
Factors that can influence your dependent variable that are not the independent variable. They lower construct validity.
What are independent measures?
When different people are used in each condition of the experiment
What are repeated measures?
When the same people are used in each condition of the experiment
What are matched participant designs?
When similar people are used in each condition of the experiment.
They can be matched on anything (apart from the IV) that will influence the DV (e.g age, gender, IQ).
What are the strengths of independent measures?
- As the participants in each condition are unaware of the other they will show reduced demand characteristics
- No order effects as only take part in one condition
What are the weaknesses of independent measures?
- Effort to collect more participants
- Findings may be influenced by participant variables
What are the strengths of repeated measures?
- As participants takes place in both conditions we can remove the effect of any participant variables
- Easier to obtain sample as you need fewer participants
What are the weaknesses of repeated measures?
- Demand characteristics - participants may identify what the study is predicting and behave accordingly (lowering construct validity)
- Order effects may influence results unless counterbalanced
What are order effects?
When participants do better/worse in the second condition due to practice/fatigue. Counterbalancing can solve this issue by reversing the order of conditions for some of the participants.
What are the weaknesses of matched participants?
- Effort to conduct a pretest and match participants
- Cannot control all extraneous variables by perfectly matching participants
What are the strengths of matched participants?
- Reduced effects of participant variables
- No order effects as different participants for each condition
- Lower chance of demand characteristics as participants only do one condition
What are demand characteristics?
When participants try to work out the aim of the study and as a result change their behaviour
What is researcher bias?
When the researcher influences the participant’s behaviour or responses
What is a single blind proceedure?
Participants are unaware what condition they are in (e.g they are unsure if they getting a regular or decaf coffee)
What is a double blind proceedure?
BOTH the participants and researchers are unaware who is in each condition
What is an alternative hypothesis?
There will be a significant difference in the DV between the IV groups.
What is a null hypothesis?
There will be no significant difference in the DV between the IV groups. Any difference will be due to chance factors.
What is a two tailed alternative hypothesis?
There will be a significant difference in the DV between the IV groups
Predicts a significant difference only
What is a one tailed alternative hypothesis?
The XX group will be significantly better than the XXX group at the DV
Predicts a significant difference AND the direction
What is operationalising?
Deciding how you wish to measure the variables within psychological research.
What is the target population?
The group of people the researcher wishes to study and apply the findings to
What does a sample being generalisable refer to?
The sample should be diverse enough to be applied to the wider population
Why does a sample want to be large?
Enough people to establish a consistent effect (external reliability)
What is a self-selecting sampling method?
Participants volunteer to take part in the study.
What is an opportunity sampling method?
Participants are obtained at the time and place of the research.
What is a snowball sampling method?
Participants suggest other people to take part.
What is a random sampling method?
Every member of the target population has an equal chance of being selected as a participant.
What are the strengths of Self Selecting sampling?
- Easy to obtain
- Already give consent to participate and more likely to continue for entirety of study
- No researcher bias as participants volunteer
What are the weaknesses of Self Selecting sampling?
- Unrepresentative sample - unemployed, keen on psychology etc (low population validity)
- Expensive if there is a money incentive
- Could mean a small sample size if lack of volunteers
What are the strengths of opportunity sampling?
- Easy to obtain at the time of the study
- Good way of obtaining target population (depending on where/when you go)
What are the weaknesses of opportunity sampling?
- Unrepresentative sample (low population validity) depending on where and when you go
- Researcher bias as the researcher can approach a certain type of person
What are the strengths of snowball sampling?
- Easy to obtain sample (especially if difficult target population)
What are the weaknesses of snowball sampling?
- Not able to generalise sample - family and friends often have similar characteristics
What are the strengths of random sampling?
- Everyone has an equal chance of being selected
- Representative of target population
What are the weaknesses of random sampling?
- Everyone has an equal chance of being selected (which can mean outliers)
- Sometimes hard to ensure all gave an equal chance
- Selected people may not be willing to take part
- Effort
What is primary data?
Data is obtained by the researchers directly.
E.g measuring reaction times of participants
What is secondary data?
Data is obtained using another source.
E.g getting information from the local council about parking violations
What is quantitative data?
Data represented by numbers such as scores or ratings.
What is qualitative data?
Data represented by words such as quotes or observations.
What are the strengths of quantitative data?
- Easy comparisons to be made between participants/conditions
- No researcher bias (can’t interpret multiple ways)
Easy to summarise (using graphs, averages etc) - Easier to establish reliability of results
What are the weaknesses of quantitative data?
- May not be representative of a participants’ everyday behaviour - low ecological validity
- Doesn’t tell us why participants behave/feel that way
What are the strengths of qualitative data?
- More detail about participant experience
- Richer data to improve validity of results (can tell us more detail on why they behaved that way)
What are the weaknesses of qualitative data?
- Harder to compare participants/conditions
- Cannot present in a graph
- Harder to analyse
- Can have researcher bias (e.g can be interpreted multiple ways)
What is raw data?
The data collected in a study before analysis takes place
What are descriptive statistics?
Ways to summarise the findings of a study (such as averages and graphs)
What are measures of central tendency?
Averages of the results
(mean, median and mode)
What are measures of dispersion?
Measures of how spread the data is
(range, variance and standard deviation)
What are inferential statistics?
Statistical tests to find out if the significance of results
(we’ll do these next year)
What is the mean?
When you add up participant’s scores/responses and divide by how many there are
What is the median?
When you place the data in order and select the middle value
What is the mode?
When you find the most commonly occurring value within the results
What are the strengths of the mean?
- Involves all the data which means more representative findings
What are the weaknesses of the mean?
- Includes outliers which may skew result
- Can give us decimal figures (which may not make sense depending on the DV)
What are the strengths of the median?
- Discounts outliers so not skewed
What are the weaknesses of the median?
- Does not include all data collected
- May be a decimal figure (which may not make sense depending on the DV)
What are the strengths of the mode?
- Easy to calculate
- Always a whole value
- Can be done with qualitative data (finding most commonly said words)
What are the weaknesses of the mode?
- May be none or more than one mode (which may not be helpful)
- Doesn’t include all data points
What is the range?
Tells you the spread between the minimum and maximum values
When you take the smallest value away from the largest value
What is variance?
Tells you the spread of each value from the mean
When you find the differences between the scores and the mean score, square them, add them up and finally divide by the number of participants minus one
What is standard deviation?
Tells you the spread of the data in relation to the mean
When you square root the variance
What are the strengths of the range?
- Easy to calculate
- Does show the spread between the minimum and maximum values
What are the weaknesses of the range?
- Does not show if the spread is even
*Can be skewed by outliers - Does not Include all data
What is the variance formula?
s2=1n−1n∑i=1(xi−¯x)2
The square of the standard deviation
How do you calculate the variance?
To calculate the variance, you first of all need to calculate the mean score for each condition in the experiment.
For each participant, you then subtract the mean score from their score. This is ‘d’ (the difference). Don’t worry if the number is positive or negative!
Then, you square each ‘d’ score. (d2)
Add up all the d2
Divide this total by n-1
What are the strengths of calculating the variance?
- Takes into account all values in the data set
- Less likely to be affected by outliers (by calculating differences)
What are the weaknesses of calculating the variance?
- More time consuming to calculate
- Not in the same units as the original measure (e.g now in cm²)
How do you calculate standard deviation?
To calculate the variance, you first of all need to calculate the mean score for each condition in the experiment.
For each participant, you then subtract the mean score from their score. This is ‘d’ (the difference). Don’t worry if the number is positive or negative!
Then, you square each ‘d’ score. (d2)
Add up all the d2
Divide this total by n-1
Square root this value
What are the strengths of standard deviation?
- Same units as original measure
- Easy to calculate if variance already done!
What are the weaknesses of standard deviation?
*Takes into account extreme outliers
