Data handling and analysis

• What is Qualitative Data?


  Data that is expressed in words and is non-numerical
• What is Quantitative Data?

  Data that is numerical
• What are qualitative methods of data collection?

  Interview or unstructured observations
• Quantitative methods of data collection

  Questionnaires, observations
• What is Primary data?

  Information that has been obtained first hand by a researcher for the purposes of a research project
• What is Secondary Data?


  Information that has already been collected by someone else
• Examples of primary data

  Questionnaires, interviews or observations
• Examples of secondary data

  Journal articles, book or websites
• AO3 Qualitative Data

  • Qualitative data offers more detail than quantitative data. It is much broader in scope and gives the PP the opportunity to fully report their thoughts and opinions on a given subject
  • Tends to have greater external validity as it provides the researcher with more meaningful insight
  • Qualitative data is often difficult to analyse as it can't be summarised statistically so that patterns and comparisons within and between data may be hard to identify
  • Conclusions often rely on the subjective interpretations of the researcher and these may be subject to bias
• AO3 Quantitative Data

  • Quantitative data is relatively simple to analyse so the comparisons between groups can be easily drawn
  • Data in numerical form tends to be more objective and less open to bias
  • Quantitative data is much narrower in meaning and detail than qualitative data so may fail to represent ‘real life’.
• AO3 Primary Data

  • The main strength of primary data is that it is authentic data obtained from the PPs themselves for the purpose of a particular investigation
  • Questionnaires and interviews can be designed in such a way that they specifically target the information that the researcher requires
  • To produce primary data it requires time and effort on the part of the researcher
  • Conducting an experiment requires considerable planning, preparation and resources compared to secondary data which may be accessed within a matter of minutes
• AO3 Secondary Data

  • Secondary data may be inexpensive and easily accessed requiring minimal effort
  • When examining secondary data the researcher may find that the desired information already exists and so there is no need to conduct primary data collection
  • There may be substantial variation in the quality and accuracy of secondary data so information may appear to be valuable but may be outdated or incomplete
  • The content of the data may not quite match the researcher’s objectives so this may challenge the validity of any conclusions
• Meta Analysis

  • The process of combining the findings from a number of studies on a particular topic with the aim being to produce an overall statistical conclusion based on a range of studies.
• AO3 Meta Analysis

  • A form of research method that uses secondary data is meta-analysis
  • This refers to a process in which a number of studies are identified which have investigated the same aims
  • The results of these studies can be pooled together and a joint conclusion produced
  • Meta-analysis allows us to create a larger, more varied sample and results can then be generalised across much larger populations increasing validity
  • Meta-analysis may be prone to publication bias as researchers may not select all relevant studies choosing to leave out those studies with negative results
• Descriptive Statistics


  The use of graphs, tables and summary statistics to identify trends and analyse sets of data
• Measures of central tendency

  Any measure of the average value in a set of data e.g mean, median and mode
• Mean

  Adding all the values and then divide by how many data sets there are
• Median

  Ranking all the data values from lowest to highest and finding the middle value
• Mode

  The most frequently occurring value in a set of data
• AO3: The Mean

  • The mean is the most sensitive of the measures of central tendency as it includes all of the values in the data set within the calculation
  • This means it is more representative of the data as a whole
  • The mean is easily distorted by extreme values and does not then represent the data as a whole
• AO3: The Median

  • The strength of the median is that extreme scores do not affect it
  • It is also easy to calculate (once you have arranged the numbers in order)
  • It is less sensitive than the mean as the actual values of lower and higher numbers are ignored and extreme values may be important
• AO3: The Mode

  • Although the mode is easy to calculate it is not that helpful
  • When there are several modes in a data set this is then not a very useful piece of information
  • For some data such as data in categories the mode is the only method you can use
  • For example, if you asked your class to list their favourite dessert the only way to identify the most ‘typical’ or average value would be to select the modal group
• Study Tip to know which measure of central tendency to use

  • If you have to decide what method of central tendency should be used with a particular set of data consider whether there are any extreme scores- a score that is significantly lower or higher than the others
  • If there are no extreme scores then the mean is the best option as it is the most sensitive measure of the three
  • However, if there is an extreme score, the median is most suitable as the mean would become distorted
  • The mode is never the best option, except if the data is in categories
• Measures of dispersion


  Term for any measure of spread or variation in a set of scores
• Range


  A simple calculation of the dispersion in a set of scores which is worked out by subtracting the lowest score from the highest score and usually adding 1
• Standard Deviation


  A sophisticated measure of dispersion in a set of scores which tells us how much each score deviates from the mean
• AO3: The Range

  • The advantage of the range is that it is easy to calculate
  • It only takes into account the two most extreme values, and this may be unrepresentative of the data set as a whole
  • The range also does not indicate whether most numbers are closely grouped around the mean or spread out – whereas the standard deviation does show this aspect of dispersion
• AO3: The Standard Deviation

  • Is a single value that tells us how far scores deviate from the mean so the larger the standard deviation the greater the spread within a set of data
  • A large standard deviation may suggest a few anomalous results due to the big spread of data and a low standard deviation value may reflect that the data is tightly clustered around the mean which might imply that PPs responded in a similar way
  • The standard deviation is a much more precise measure of dispersion as it includes all values within the calculation
  • But it can be distorted by extreme values
• Scattergram


  A type of graph that represents the strength and direction of the relationship between co-variables in a correlational analysis
• Bar Chart

  A type of graph in which the frequency of each variable is represented by the height of the bars
• How to draw a bar chart?

  • Bar charts are used when data is divided into categories
  • The categories occupy the horizontal x-axis
  • The frequency or amount of each category is plotted on the vertical y-axis
  • Bars are separated on a bar chart to denote that we are dealing with separate conditions
• How to draw a histogram?

  • The bars touch each other which shows that x-axis data is continuous
  • The x-axis is made up of equal-sized intervals of a single category
  • The y-axis represents the frequency within each interval. If there was a zero frequency for one of the intervals the interval remains but without a bar
• When drawing a graph what are some main things you need?

  • The x and y axis labelled
  • Title
  • Make sure intervals are all correct
• Normal Distribution

  • Normal distribution is a bell shaped curve which is symmetrical
  • Most people are located in the middle area of the curve with very few people at the extreme ends
  • The mean, median and mode all occupy the same midpoint of the curve
• Normal Distribution

  Normal distribution

  
• Positive Skew

  • Where most of the distribution is concentrated towards the left of the graph, resulting in a long tail on the right
  • The mean remains at the highest point of the peak
  • The median comes next
  • Last is the mode
• Negative Skew

  • Long tail is on the left hand side with most of the data distributed on the right
  • The mode is the highest
  • Then the median
  • The lowest is the mean
• Correlation


  Investigating an association between 2 co variables
• What are correlations plotted on?

  Scatter graphs
• What values can a correlation be?

  Between -1 and 1