Using Descriptive Statistic Test in Research
This easy tutorial will show you how to run the descriptive statistic test in SPSS, and how to interpret the result.
Descriptive statistics are used to describe the basic features of the data in a study. They provide simple summaries about the sample and the measures. Together with simple graphics analysis, they form the basis of virtually every quantitative analysis of data. (Source)
The most used procedure in descriptive statistics is to calculate measures of central tendency and measures of variability.
Central Tendency Measures
Central tendency measures are the most calculated measures in descriptive statistics. These measures describe the “central”, “most common” or “average” result in a set of results, i.e. talk about the value around which the sample results are grouped.
The most used central tendency measures are: mean, mode, and median.
The mean is the most calculated measure of central tendency, and many statistical techniques use the mean in inference statistics. It represents the average score in some distribution of results. It is the quotient of the sum of all scores and their number moreover it is calculated for the interval or ratio level of measurement.
The mode is the most observed score in a distribution. It is the only measure of central tendency that can be applied to nominal data, and can also be used to ordinal, interval, and ratio data.
The median of a distribution with a discrete random variable depends on whether the number of terms in the distribution is even or odd. If the number of terms is odd, then the median is the value of the term in the middle. This is the value such that the number of terms having values greater than or equal to it is the same as the number of terms having values less than or equal to it. If the number of terms is even, then the median is the average of the two terms in the middle, such that the number of terms having values greater than or equal to it is the same as the number of terms having values less than or equal to it. (Source)
Variability measures describe the variability or dispersion of results around the center. Results dispersion refers to the range of results and the limits of the range. The most used variability measures are range, quartiles and percentiles, variance, and standard deviation.
Percentiles divide the distribution of results into 100 parts, i.e. each part contains 1% of the distribution results. Since the median is the central result in the distribution, it is equal to the 50th percentile.
The quartiles divide the distribution into four equal parts, each part containing 25% of the distribution results.
The range is the difference between the maximum and minimum.
Variance and Standard Deviation
Variance and standard deviation are the most used measures of variability. The standard deviation is the square root of the variance.
An Example: How to Run the Descriptive Statistic Test in SPSS
We used a data sample that consists of five variables: wage (annual wages in dollars), industry (industry of employment), occupation (respondent’s occupation), age (age in years), responsibility (job responsibility), and gender.
For nominal and ordinal variables, we will use Frequencies, while for interval or ratio variables we will use Descriptives.
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