? Correlation and regression are techniques which are used to see whether a relationship exists between two or more different sets of data Learning Objectives: To identify, by diagram, whether a possible relationship exists between two variables; To quantify the strength of association between variables using the correlation coefficient; To show how a relationship can be expressed as an equation; To identify linear equations when written and when graphed; To examine regression, a widely used linear model, and to consider its uses and limitations. Scatter Diagrams
Perfect positive correlation exists between the data. If x is known y can be predicted exactly. +0. 8 < +1Strong positive correlation exists between the data. As x increases y increases. Interpretation of r +0. 4 < +0. 8Moderate positive correlation exists between the data. As x increases y increases -0. 4 < +0. 4Very little correlation exists between the data -0. 4 < -0. 8Moderate negative correlation exists between the data. As x increases y decreases. Interpretation of r -0. 8 < -1Strong negative correlation exists between the data. As x increases y decreases. -1 Perfect negative correlation exists between the data.
The Essay on Data Table Analysis
This brief will evaluate the design elements of the data tables from an accounting perspective for Kudler Fine Foods. An entity relationship diagram illustrating the existing data tables will be created. Recommendations that are needed for improvements to the data tables will also be outlined. This brief will show a pivot table using Kudler’s general ledger inventory data and there will be an ...
If x is known y can be predicted exactly. Regression Regression is a technique which builds a straight line relationship between two sets of data. This relationship is of the form y = a + bx where a and b are found by the following formulae b = n? xy?? x? y n? x2-(? x)2 EXCEL:=SLOPE(Y DATA, X DATA) a = ??? y- b? x n n EXCEL:=INTERCEPT(Y DATA, X DATA) Example 4. 5 – Calculation of a and b To calculate use Summary values from Correlation Calculation: i. e. ?y 255 ?x 80 ?x2 756 ?y2 7097 ?xy 2289 n 10 SLOPE: b = n? xy – ? x? y = (10*2289) – (80*255) n? x2-(? x)2 (10*756) – (80)2 b = 22890 – 20400 = 2490 7560 – 6400 1160
b = 2. 1465517 INTERCEPT: a = ?y – b? x = 255 – 2. 1465517 * 80 n n 10 10 a = 25. 5 – 17. 172413 = 8. 327587 Example 4. 5 – Calculation of a and b The final answers (rounded to three decimal places) are: a = 8. 328 b = 2. 147 (note that 3 decimal places were chosen as the data supplied were in thousands and hundreds) These give the linear regression equation y = 8. 328 + 2. 147x or, if preferred, sales = 8. 328 + 2. 147*advertising expenditure Forecasts Forecasts may be made using the resulting model. If the x (independent) value used falls within the original data set then this forecast is known as interpolation.e. g. Advertising expenditure = ? 700 (inside original range) i. e. x = 7 giving y = 8. 328 + 2. 147 * 7 = 23. 357 i. e. 23,357 sales are forecast If the x value falls outside the bounds of the original data then this forecast is known as extrapolation and care must be taken in its use. Expenditure = ? 1800, so x = 18 y = 8. 328 + 2. 147 * 18 = 46. 974 i. e. , 46,974 sales are forecast Coefficient of Determination The coefficient of determination (r2) is another measure which may be used to assess the appropriateness of a regression model.
This is found by squaring Pearson’s correlation coefficient and then expressing as a percentage. The resulting figure is then used to describe the percentage variation in the y data which can be attributed to the variation in x data. In the Sales – Adv. Costs example r = 0. 948 so r2 = 0. 899 So it may be said that 89. 9% of the variation in sales of the products is due to variation in the levels of advertising expenditure. Rank Correlation i. e. Spearman’s Used to assess evidence of a relationship between two sets of data, at least one of which has been ranked in some way.
The Essay on Data on Sale
1. Do data brokers pose an Ethical Dilemma? Explain your answer. Answer: Data brokers have both negative and positive social impact as such they pose an ethical dilemma. In one hand, from the case, we know that information that data brokers provide or sell to its customers like Internal Revenue Service and Department of Homeland Security and Justice have used for law enforcement and ...
