When it comes to psychology and many other subjects, you will probably notice that results are often written and displayed in the form of tables, charts and graphs in research. The purpose of this is to allow readers to interpret and visually understand the study results easily.
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Jetzt kostenlos anmeldenWhen it comes to psychology and many other subjects, you will probably notice that results are often written and displayed in the form of tables, charts and graphs in research. The purpose of this is to allow readers to interpret and visually understand the study results easily.
Data analysed in research is often displayed in three ways:
Various forms of tables, charts and graphs in research are used to display results. The type of table, chart or graph used is determined by what the researcher wants to illustrate and the type of test used to obtain the results. Let's discuss this in more detail.
The purpose of frequency tables and diagrams is to visually show how often a variable is observed and occurs in research. For instance, frequency tables and diagrams may be used to show the frequency of colour preferences. To do this, researchers need to list each variable on a table and tally how often reports the colour.
An example of how a frequency table may look is shown below.
Colour preference | Frequency |
Red | III |
Blue | IIII |
Pink | III |
Green | I |
From the frequency table shown, it is apparent that most participants reported blue (four) as their favourite colour, and the least amount of people said green (one) as their favourite colour.
Bar charts and histograms are often confused. Although they may look similar, i.e. they both have bars, there are many differences between them. For instance, they display different information, and there are gaps between the bars in bar charts but not in histograms.
Bar charts are a form of frequency diagrams, and they can be used to display frequency tables in graph form. Bar charts show the frequency of nominal or categorical data.
Nominal data has no meaningful order, and each variable is exclusive, meaning participants can give only one response, e.g. if they like pink or blue. Nominal data is represented items that can belong to a category; for instance, favourite drinks can be given options such as tea, coffee, soda, juice, and water, aka nominal data.
Categorical data can be divided into groups such as gender, ethnicity or socioeconomic status.
When plotting the data on graphs, the frequency should be plotted along the y-axis, and the variables should be listed on the x-axis.
Each bar on the chart represents how often each variable is observed. Between each bar, there is always a gap to show that each variable is distinct from the others. For example, pink and blue are different responses, and participants can only report one or the other.
The taller the bar, the higher the frequency/occurrence of the variable and the shorter the bar, the lower the frequency/occurrence of the variable.
Histograms, similar to bar charts, are used to display data visually. In addition, to bars being of differing heights, each bar can vary in width, and the area of each bar represents the frequency of each grouped data. Before data is plotted on a histogram, a calculation must be done to group data.
Histograms are used to show how data for each variable is distributed, whereas bar charts are used to show how frequently a variable occurs. Whether data is normally distributed or not determines later statistical tests that could be used. Histograms are often used to analyse numerical data that is non-discrete.
Numerical, non-discrete data is continuous data that can have an infinite number of values.
When the bars in a histogram take the shape of a bell curve, the mean and median of the data can be considered approximately the same. The data can be deemed to have a normal distribution.
When the tallest bars, which get shorter across the x-axis, are shifted to the histogram's left, the data is positively skewed. Typically the mean is thought to be larger than the median. The data is negatively skewed when the bars go from short to taller across the x-axis. Typically this suggests that the median is greater than the mean.
Most researchers aim to collect normally distributed data, as it is more representable and valid.
We will learn about how to complete a histogram through the use of an example. Let's start by taking a look at the table below.
Age | Frequency | Lower class limit | Upper-class limit | Class interval |
25 - 30 | 3 | 25 | 30 | 30 - 25 = 5 |
31 - 38 | 6 | 31 | 38 | 38 - 31 = 7 |
39 - 45 | 4 | 39 | 45 | 45 - 39 = 6 |
46 - 50 | 2 | 46 | 50 | 50 - 46 = 4 |
The table is called a frequency distribution table, the lower class limit is the lowest value in the class, and the upper class is the highest value. The class interval is calculated by measuring the difference between the upper and lower class limit.
To plot a histogram, the next step is calculating each bar's height. To do this, you need to divide the frequency by the class interval; this value is known as frequency density.
For the 46-50 age group, the frequency density would be calculated as 2 / 4 = 0.5.Frequency Density = Frequency / Class Interval
Once the frequency density is known, the data can be plotted onto a histogram. On the x-axis, each age (25-50) would be listed, and frequency density would be labelled along the y-axis.
Pie charts are used when researchers want to highlight the proportions of data. Pie charts allow readers to easily identify the differences between the proportions of variables via the visual diagram.
Let's take the following tables as an example to help understand how pie charts are constructed:
Colour Preference | Frequency | Degrees for each segment of the pie chart |
Yellow | 5 | 5/18 * 360 = 100 |
Blue | 3 | 3/18 * 360 = 60 |
Pink | 6 | 6/18 * 360 = 120 |
Purple | 4 | 4/18 * 360 = 80 |
The number 360 is used because a circle always is 360o. If you add all the numbers listed under the Degrees for each segment of the pie chart headline, you will see that all the angles summed together equal 360.
The pie chart below is what it should look like!
The pie chart shows that most participants consider pink their favourite colour, and blue is the least popular preference.
To finish up discussing the different types of tables and graphs in research, let's talk about scatter diagrams. Scatter diagrams are used to illustrate the results of correlational tests. Correlations aim to identify if there is a relationship/ association between two variables.
A hypothetical study may measure the association between studying time and exam grades. Each participant's score will be plotted onto the scatter diagram (this should reflect how long they studied and the grade they scored on a test). When plotting a scatter diagram, the data points are never connected.
From scatter diagrams, we can identify the strength of the association and the direction of the relationship between the two variables.
Tables, charts and graphs in research are used to visually display research findings.
There are different types of charts, tables and graphs in research, and each one can be read and interpreted differently. For example, the strength and direction of data points in scatter diagrams are used to interpret correlations between two variables.
Graphs are commonly included in psychological reports to visually display the results collected from a study.
Tables, charts and graphs are different techniques that researchers use to aid the understanding of their research findings.
Charts and graphs are used in psychology because many find it easier to understand data when it is displayed in pictorial form.
How do you calculate frequency density?
Divide the frequency by the class interval
What information does a scatterplot tell us about the association between two variables?
What type of test is usually carried out when a scatter plot has been carried out?
Correlation
Data is ______ skewed when the median is found to be larger than the mean.
Negatively
Data is ______ skewed when the mean is found to be larger than the median.
Positively
What is the shape of a histogram that is negatively skewed?
When the bars go from short to taller across the x-axis, the data is negatively skewed.
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