İSTATİSTİK I

Dot plot is almost the easiest of the graphs. It can be drawn by hand easily while collecting data. Dot plot will be very useful when the number of objects in our study is rather small such as up to 50 observations. Dot plot is generally used to investigate univariate (quantitative) data, but sometimes it is used to compare two variables. Essentially a dot plot is a one-dimensional scatterplot of observed values of a variable. In order to create a dot plot one needs to identify the lowest and the highest value of the data set first, then a horizontal axis is drawn and scaled so that it covers the lowest and highest values.

There are 3 female students who got 70 and 3 who got 75, which is the highest number of females around these grades.

A stem-and-leaf display is a type of graph for listing the numerical data and very similar to dot plot. If you remember in dot plot, dots are used to represent the each observation in our data. In stem-and-leaf display the original numbers are kept and a visual representation of data is created.

A pie chart is usually used for categorical data. Line chart is often used to display the trends in a continuous data over a period of time.

One advantage of the stem-and-leaf display is that it gives the researcher a chance to create a grouped frequency distribution of the data without using any formula.

The stacked bar chart is a bar chart where each bar is divided into subgroups proportional to the contribution a subgroup makes to associated bar.

Histogram is a graph that is very similar to a bar chart except that bar charts are drawn for qualitative data but histograms are drawn for continuous data. Histograms will help us to identify the center, shape and symmetry of the data. A histogram can tell us about the peaks and extreme values, whether the distribution of data is skewed to the left, skewed to the right, bell-shaped, uniform or bimodal. A histogram can also be used to check out the normality.

In economics, the tendency of a foreign currency versus Turkish Lira may also be analyzed by a simple line chart, which may show a long term increase in the value of Turkish Lira against the foreign currency of interest. Therefore, an investor may decide that the power of Turkish Lira is increasing and it is high time to make an investment in Turkey.

Scatter plot is used to investigate the relationship between two variables. They are also very helpful indicating the minimum, maximum or outliers of the variables. One of the reasons that the scatter plots may be drawn is that scatter plot gives a good indication about the correlation between two variables.

In this figure, the scattered data points indicate a negative correlation between two sets of data, here the values of y-axis are decreasing but as it decrease the values of the y-axis variable increases.

This pattern indicates that the days with high humidity tend to have temperatures at 2 C degrees, 5 C degrees and 8 C degrees.

A properly created graph can report various information of the data in a visual form. For instance, the shape of the distribution of the data, the relation between two sets of data, the most repeating observations, outliers, peaks, summary statistics (minimum, maximum, range, mean, median) etc. can be identified from graphics.

Dot plot is almost the easiest of the graphs. It can be drawn by hand easily while collecting data.
Dot plot will be very useful when the number of objects in our study is rather small such as up to 50
observations. Dot plot is generally used to investigate univariate (quantitative) data, but sometimes it is
used to compare two variables.

In order to create a dot plot one needs to identify the lowest and the highest value of the data set first, then a horizontal axis is drawn and scaled so that it covers the lowest and highest values. A dot plot, essentially, is a simple chart where each observation is presented by a dot along the horizontal axis. If there are repeating observations (multiple occurrences), the dots are stacked up vertically. The dot plots will produce a simple graph of data but at the same time the data itself is never lost, you can easily identify the value of any data point in the dot plot. This is the most powerful aspect of the dot plots. It allows the researcher to show the data in a pictorial form without losing the original information/data. It also gives an opportunity to the researcher to quickly order the data.

In stem-and-leaf display the original numbers are kept and a visual representation of data is created. Basically, stem-and-leaf display divides the values into a stem and leaf using a vertical line. The “stem” represents the greatest digits on the left of the line where the right of this line displays the “leaf ” with the remaining digits. This graph can be useful to figure out the range, outliers, the most frequent values and the shape of the data. It is also useful for assessing the location and spread of the distribution of the data.

If you want to create a stem-and-leaf display of this data, you need to decide what the stem should be, it is easy to see that all these numbers are the multiples of ten, so the numbers should be 14, 15, 16, and 17. Stems and the leaves should be ordered on each stem from smallest to largest. A vertical line/axis is drawn and on the left hand side of the line/axis stem values are shown as a new row, next we start putting each observation to the right hand side of vertical line according to trailing digits. At last step in each row, the numbers on the right hand side is ordered. Thus the stem-and-leaf plot should be 

Simple bar chart is used to represent discrete values for each category for a given variable on x-axis (horizontal). The y-axis (vertical) shows the actual numbers that are the bar heights for the corresponding category. Thus, the graph should be;

 

DeA pie chart is usually used for categorical data. In pie chart components or outcomes of a total frequency is shown as sectors of a circle. The shape resembles to a pie, hence the name of the chart. In pie chart, the categories are divided in to slices/sectors. Each slices’ size is proportional to the total number of objects. The drawing of a pie chart involves the calculation of angles for each slice/sector. Find the calculation table and the chart below.

Bar chart or sometimes called bar graphs are typically used to compare counts, frequencies, total number of categories, objectives, amounts etc. It is used for the graphical representation of the qualitative data. Bar chart is the graphical representation of frequencies by rectangles (or bars) with lengths (or heights) proportional to the frequencies of observations. Depending on the variable type and grouping, it is possible to create many types of bar chart

Simple bar chart is used to represent discrete values for each category for a given variable on x-axis (horizontal). The y-axis (vertical) shows the actual numbers that are the bar heights for the corresponding category.

The stacked bar chart is a bar chart where each bar is divided into subgroups proportional to the contribution a subgroup makes to associated bar. Likert type items are often represented by stacked bar chart.