Scatter plot- Complete
- 1. Scatter Plot BY IRFAN YAQOOB
- 2. Content To discuss Scatter Plot
- 3. Learning Objectives At the End of this presentation We will get brief ideas about Scatter Plot create a scatterplot to graphically depict the relationship between 2 quantitative variables describe the information that a scatterplot conveys about the relationship between 2 quantitative variables: form, direction, strength etc.
- 4. Continue.. calculate the correlation coefficient between 2 quantitative variables using technology. interpret the value of the correlation coefficient How to draw in Excel 2013
- 5. Scatter Plot Background… On numerous occasions, our interest lies not in just one single variable but in two, three, four or more variables. For example, if we talk about the yield of a crop, we realize that the yield of any crop depends on a variety of factors --- the fertility of the soil, the type of fertilizer used, the amount of rainfall, and so on. Now we discuss about bivariate variable.
- 6. Scatter Plot A scatter plot is a graph of a collection of ordered pairs (x,y). The graph looks like a bunch of dots, but some of the graphs are a general shape or move in a general direction.
- 7. Example An important concern for any pharmaceutical company producing drugs is to determine how a particular drug will affect one’s perception or general awareness. Suppose one such company wants to establish a relationship between the PERCENTAGE of a drug in the blood-stream and the LENGTH OF TIME it takes to respond to a stimulus. Suppose the company administers this drug on 5 subjects and obtains the following information:
- 8. Example Continue… Subject % of drug (X) Reaction Time (Y) A 1 1 B 2 1 C 3 2 D 4 2 E 5 4
- 9. Example Continue… In this example, the reaction time to the stimulus will DEPEND on the amount of drug in the blood-stream So we draw the Scatter Plot for this and it will be like this.
- 10. Why we Use Scatter Plot TO find outlier When we have a pair of numeric data Correlation Identify the type of relationship between two quantities.
- 11. Correlation is a measure of the strength or the degree of relationship between two RANDOM variables. A numerical measure of the strength of the linear relationship between two random variables X and Y. Explanation: In correlation we have three cases Case1: Positive Correlation 0<r<1 Case1: Positive Correlation r=0 Case1: Positive Correlation -1<r<0 Where r is the coefficient of correlation
- 12. 1. A positive correlation. As one quantity increases so does the other. 2. A negative correlation. As one quantity increases the other decreases. 3.No correlation. Both quantities vary with no clear relationship. Positive Correlation Negative Correlation No Correlation
- 13. Example Suppose we want to check the relation between temperature and sales of the jackets we have following data and we draw its diagram and find it correlation Temp Sale Correlation 110 0 90 2 76 7 80 12 25 34 20 40
- 14. Example in detail Suppose that the principal of a college wants to know if there exists any correlation between grades in Mathematics and grades in Statistics. Suppose that he selects a random sample of 9 students out of all those who take this combination of subjects. The following information is obtained: Students Marks in Math Marks in Statistics A 5 11 B 12 16 C 14 15 D 16 20 E 18 17 F 21 19 G 22 25 H I 23 25 24 21
- 15. Continue… Scatter Plot for this The correlation between them is 0.78 , this shows the strong relationship between two variables.
- 16. INTERPRETATION There exists a strong positive linear correlation between marks in Mathematics and marks in Statistics for these 9 students who have been taken into consideration. The conclusion that we have just drawn i.e. strong positive linear correlation --- this conclusion is supported by the scatter diagram.
- 17. 0 < |r| <0 .3 weak correlation 0.3 < |r| < 0.7 moderate correlation |r| > 0.7 strong correlation
- 18. Tool Used We have number of tools to draw scatter plot , but in this case we use a very simple tool Microsoft Excel, because this tool is approachable to every one and easy to use as well. You can use SPSS scatter plot as well.
- 19. How to draw Scatter plot on Excel 2013 Open excel 2013 from window explorer Click on empty workbook Add your data on the workbook After adding select your data Go to INSERT tab in the bar menu There is an image for Scatter plot Click on it and it will create a scatter plot
- 20. Continue… You can set the trend line by right click on the diagram , it will show you the format plot area and you can easily draw a trend line on the relationship. Now to find the correlation click on the Data on the Menu Bar. You can see the an option of Data analysis on the top right. Click on data analysis and find correlation option draw your input and output range and correlation will be calculated.