quantative data analysis & interpretation

quantative data analysis & interpretation

1. descriptive statistics

   • form basis if quant. data collection
     • used to summarise & present sample data
       • analysis of possible relationships between variables
         • describe shape, central tendency & variablility in a data set
           • common descriptive statistics
             • frequency distributions
               • asures of central tendancy
                 • measures of dispersion

2. frequency distribution

   • first and most basic
     • a frequency distribution is a systmatic way of arranging numeric values from the lowest to highest
       • often has a count or percentage of the number of tiumes each value occured

3. measures of central tendancy

   • mean, median, mode
     • mean
       • average typical score
         • mean is the sum of all values, devided by the number of particpants
       • sensitive to extreme values
         • not appropriate for data that differs greatly
           • i.e. not bell shaped
             • if the mean differs meaningfully from the median is suggests that the distribution is skewed
     • mode
       • value that occurs most
         • mostly used for catagorical variables
     • median
       • middle value in a ranked list
         • paired with percentile and inter-quartile range
           • not sensitive to extreme values
             • if no. of observations is even, the average of the two middle observations is used

4. measures of dispersion

   • spread of data
     • are most of the values close to the mean?
       • widely spread about the mean?
         • if values are similar = low dispersion
           • wide range = dispersion high
             • type of descriptive statistic
               • describe spread of data about the mean
                 • are ways of presenting the data, spread or dispersion of data in a sample
                   • are used becuase for some sample data, measures of central tendancy alone do not provide an adequate description of the data

5. common used measures of dispersion

   • range
     • highest score minus lowest score
   • percentile
     • provide info. about the location of a score in relation to other scores
       • score is at or below a certain % of scores lying in a distribution
   • interquartile range IQR
     • quartiles- values of distribution that divide into 4 parts
       • IQR- is the difference between the 1st and 3rd quartile
         • -count 25% through list = lower quartile
           • count 75% through list = upper quartile
             • UQS - LQS = IQR
   • standard deviation
     • is the companion to the mean
       • measures the distribution from the mean value