Quasi experiments
research method where the IV changes naturally and not manipulated by a researcher. The DV is measured.
Description -The main features of experiments are:
- Involves researching a naturally changing IV
- The effect on the DV of a changing the IV is measured
- Can involve a natural experiment (natural setting) or difference study (natural or controlled setting)
- The researcher has no control over allocating participants to IV groups.
E.g. Raine et al investigated the defences in brain activity of murderers compared to non-murderers
Independent groups
Repeated measures
Dis - increase chance of demand characteristics
- order effects may occur
- inappropriate to use for a quasi experiment
Matched pair designs
Adv- controls the participant variables of participants
- no order effects
Dis- very time consuming to match up and find similar participants
- difficult to completey match participants on important characteristics therefore participant variables may affect still may have an effect
Quantitative data - interval
• Measurements are on a standardised scale of fixed units separated by equal distances
• Standardised personality and IQ scales are generally accepted as having equal distances between the units, but are sometimes referred to as ‘plastic’ scales as we cannot know this for certain
• Values can be positive or negative, e.g., temperature
• Although the scale is of equal intervals, the intervals are not always meaningful, e.g., room temperature increasing by 5 degrees is more likely to be noticed if the starting temperature is -3 degrees rather than 33 degrees
Quantitive data - ordinal
Data is placed in rank order which allows meaningful comparison
• We can make statements about the relative magnitude (size) of
nominal
• Possible to state one value is higher than another, but not to assume more than this, e.g., if people are placed in height order and given a rank of 1-10, we cannot say the tallest person is twice as tall as the person ranked fifth
Data gathered on unstandardized, invented scales, e.g., attitude scales or responses to Likert-style questions should be treated at this level
Quantitive data - ratio
• Strongest level of measurement
° Like interval scales, but measurement starts a genuine zero point.-absolute zero
• The data is represented physical quantities such as time, weight, pressure, length, wages
We can say someone who weighs 88kg is twice the weight of a person weighing 44 kg or that someone who completes a reaction time task in 32 seconds did it in half the time of someone taking 64 seconds
Quantitive data - nominal
• Weakest, most basic level of measurement
• Also referred to as ‘categorized’ or ‘frequency’ data
• People and objects are classed together on the basis of common features
• These categories are mutually exclusive: it is only possible to belong to one category
• Named categories can be given arbitrary numbers, labels or codes
Quantitative data
Quantitative research gathers data in a numerical form which can be put into
units of measurement. This type of data can be categories, or in rank order, or measured in
used to construct graphs and tables of raw data
Quantitive data examples
Data collected in experiments
Closed answer questionnaires
Observations - tallies on behaviour checklists
Content analysis - number of occurrences of categories.
Quantitative data evaluation 6 marks
Easier to analyse numerical measurements compared to descriptive qualitative data and make comparisons - this makes it easier to draw conclusions
+ Numerical data is easier to collect from a large group of participants than descriptive qualitative data. You can therefore collect more data in the time frame or it takes less time to collect the data.
May lack validity as numbers may over simplify reality, e.g. closed answer questionnaires using rating scales may not represent participants’ true feelings - therefore conclusions may be meaningless.
- Some aspects of human thought and behaviour may be difficult to operationalise in a numerically measurable form, e.g. feelings towards parents.
Qualitative data
Data which is descriptive rather than quantifie or counted, therefore it is observed or reporte rather than measured.
Qualitative data examples
Case studies - e.g. Bowlby’s 44 Juvenile Thieves study Open answer questionnaires
Observations - description of behaviours observed, e.g. Milgram’s description of the distress participants showed when administering the shocks.
Content analysis - converts qualitative data into quantitative data
Qualitative data 6 mark evaluation
+ May have high validity as qualitative data provides detailed information which provides insights into participants’ true thoughts or behaviour, therefore meaningful conclusions can be made
+ Unlike quantitative data, qualitative data represent all aspects of human thought and behaviour as it is descriptive, e.g. feelings towards parents.
Difficult to make comparisons across different groups or participants compared to numerical quantitative data as it is not uniformed and often very complex, therefore it is difficult to analyse data.
- Reduces access to a greater amount of data, as it is harder and more time consuming to collect descriptive data from large groups rather than numerical quantitative data.
Primary data
Data which is collected or observed directly by the researcher/s first hand from participants which is specifically for the purposes of the research study, using questionnaires, interviews, experiments etc. for their research.
Primary data examples
Data collected in experiments - e.g. Loftus and Palmer
Responses to questionnaires
- Observations conducted by researchers
Interviews carried out by researcher
Primary data evaluation 6 marks
The researcher controls the methods and tools
- As the researcher designs the study and collects
used to collect the data; therefore, they can
the data themselves it can be more time
ensure they specifically test the hypothesis of
consuming than using secondary data.
their study.
+ As the researcher designs the methods used to collect the data, including controlling extraneous variables etc., they can ensure internal validity.
- Can be difficult, impractical or unethical to collect large sets of data for some behaviours, e.g. national crime rates or number of mental health diagnoses across different countries.
Secondary data
Data collected indirectly by someone other than the researcher of the study whose purpose was for something other than the aims set by the researcher.
Secondary data examples
Government statistics
Meta-analysis - combining data from several different studies
Literature review -e.g. Myers & Diener (1995)
study
- Artefacts for content analvsis
Secondary data 6 mark evaluation
+ Quicker than collecting primary data as the researcher has not designed the study and collected the data themselves.
+ Can analyse data which might be impractical or unethical to collect using primary sources such as large sets of data for some behaviours like national crime rates or number of mental health diagnoses across different countries.
As the researcher does not control the design of the methods used to collect the data, including controlling extraneous variables etc., they cannot ensure the internal validity.
- The researcher does not control the methods and tools used to collect the data, therefore the data may not fully match the aims and hypothesis of their study.
Measures of central tendency: mean
How’s it calculated -To calculate this, you add up all numbers in a data set and then divide this by the number of numbers
Advs -Appropriate to use for further statistical analysis such as a standard deviation.
+
Appropriate to use for ordinal, interval and ratio levels of data.
Dis - - It is affected by extreme scores ( or low) and can
the exam you r
misrepresent the
, andard deviatic
numbers as a resur
Misleading as it ma, produce a value tha no participant in the data set achieved.
Measures of central tendency : mode
-This is calculated by counting which score occurs the most and can generate more than one modal score if there are the same number of scores for two or more numbers.
Adv- Not biased by extreme
scores
+ It can be used with nominal (categorical) data, and that it provides information about frequency.
+ Unlike the mean and median there is always a modal score in the set of data, even if it is bimodal.
Dis-It ignores values by only looking at the frequency of numbers this may lead to a biased representation as an outlier score maybe the most frequent.
- Can be unclear as the data may have several
modes (bi-modal = 2+
modes)
Measures of central tendency - median
-This is calculated by arranging scores in order and finding the mid-point
Advs-Makes use of all the values but is not as biased by extreme scores as using the mean.
+ It can use with ordinal data
Dis- More open to bias from extreme scores than the mode.
- Unhelpful for further statistical analysis such as using SD.
Measures of central tendency- range
-A measure of the spread of scores, shown by the difference between the highest and the lowest value
Advs-It’s easier to calculate than standard deviation
+ Takes into account the complete breath of values because it uses the highest and lowest scores, unlike SD.
Dis– It is affected by extreme values;
- It does not give info on whether the scores are clustered around the mean or spread out.