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Correlation

Least-Squares Regression Lines for Bivariate Data

Bivariate data for the quantitive variables x and y are given in the table below. These data are plotted in the scatter plot shown next to the table. In the scatter plot, sketch an approximation of the least-squares regression line for the data. X Y 4.2 6.7 4.6 6.2 4.5 5.5 8.6 3.4 3.6

Correlation Analysis: Significance of Correlations

Using the same sample data listed in the Background Response below, calculate the variance of the same sample data, and use that as the population variance. Use the P-Value Method for the calculations. Background: 1. Ask fifteen (15) people to estimate the distance (in miles) from Washington D.C. to New York, New York (sa

Correlation and Regression (Descriptive Statistics)

Finding the Equation of the Regression Line and Making Predictions. In each case, find the regression equation, letting the first variables be the independent (x) variable. Find the indicated predicted values. 1. Tobacco and Alcohol in Children's Movies: Refer to data Set name Children movies and use the times that the

Scatter Diagram Characteristics

A graph that shows the pattern of the relation of two variables is a scatter diagram. How would you define or describe a scatter diagram? When making a scatter diagram, the lowest value on the horizontal axis us usually what value? The overall shape of a scatter diagram should be roughly square. What is the difference between

Methods of Computation and Correlation Lines

Make up a scatter diagram with 10 dots for each of the following situations: (a) perfect positive linear correlation, (b) large but not perfect positive linear correlation, (c) small positive linear correlation, (d) large but not perfect negative linear correlation, (e) no correlation, (f) clear curvilinear correlation. Not

Testing for serial correlation

Membership on a stock exchange for five years is given below: year members 1996 520 1997 510 1998 505 1999 508 2000 512 Use the exponential smoothing procedure to obtain estimates of the trend (this is not the logarithm approach here. Set the smoothed value for 19

Descreptive Statistics - Correlation

A researcher demonstrated a correlation of .60 between teacher attire and student academic performance across 150 grade schools in her state. She concluded that encouraging teachers to be properly attired will increase academic performance. Based on your professional roles, briefly describe three correlational studies you

Correlation/Coefficient

1. Which is the weakest correlation? a. +0.76 b. +0.21 c. -0.01 d. -0.88 2. What would a correlation of .35 would be called? a. Moderate b. Weak c. Very Strong d. Very Weak 3. Which correlation coefficient indicates the strongest relationship? a. 0.00 b. +0.50

Spearman Rank correlation in SPSS

A common concern for students and teachers is the assignment of grades for essays or term papers. Because there are no absolute right or wrong answers, these grades must be based on a judgment of quality. To demonstrate that these judgments actually are reliable, an English instructor asked a colleague to rank-order a set of t

Point Biserial Correlation

To test the effectiveness of a new studying strategy, a teacher randomly divides a sample of 8 students into tow groups, with n = 4 in each group. The students in group one receive training in the new studying strategy. Then all students are given 30 minutes to study a chapter before taking a quiz. The quiz scores for the t

Cholesterol and Body Mass Index

Cholesterol and Body Mass Index: use the following data set below and use the cholesterol levels (x) and body mass index values (y) of the 40 women. a.Based on a scatter plot, describe the relationship between the variables. b.Find r-squared and use it to determine the value of the correlation coefficient. Is the correl

Which types of analysis does human service research use the most?

The researcher usually conducts one of 3 types of analysis, a statistical comparison, correlation or predictions. Each of these techniques provides a unique perception of the findings. Which technique do you think is used most often in human service research and why?

Determine independence and find correlation

The Joint PMF of the pair of random variables (X1,X2) is given by: f(x1,x2) = (x1x2/35) + (2x1/35) + (x2/35) +(2/35) ; x1=1,2 x2= 1,2 a. Are X1 and X2 Independent? Justify b. What is the p= correlation(x1,x2) p= rho sign

Hypothesis test: correlation coefficient

Coastal State University is conducting a study regarding the possible relationship between the cumulative grade point average and the annual income of its recent graduates. A random sample of 151 Coastal State graduates from the last five years was selected, and it was found that the sample correlation coefficient between cumul

Sample correaltion coefficient

The number of convertibles sold at a car dealership in a month and the average monthly temperature (in degree Fahrenheit) are given in the Table below : Convertible sold, x 0 2 6 5 7 9 Average monthly temperature, y 40 48 58 62 72 79 Find the sample correlation coefficient r? Determine whether there is a positive

Finding sample correlation coefficient

Problem: For major league baseball teams, Is there any relationship between player payroll and mean attendance? Player Payroll Mean Attendance 1000,000 in thousands X Y Anaheim 62.8 28.52 Balfimore 56.5 33.09 Boston 110.2

Statisics - Scattered diagrams and linear correlation

The following data are based on information from Domestic affairs. Let X be the average number of employees in a group helh insurance plan, and let Y be the average administrative cost as a percentage of claims. X: 3, 7, 15, 35, 75 Y: 40, 35, 30, 25, 18 a) Make a scatter diagram and draw the line you think best fits the d

Correlation, causation, and lurking Variables

Over the past decade, there has been a strong positive correlation between teachers salaries and prescription drug cost. a) Do you think that paying teachers more causes prescription drugs to cost more? Explain. b) What lurking variables might be causing the increase in one or both of the variables? explain.

Linear correlation coefficient

Given the following ordered data pairs (x, y), compute the value of the linear correlation coefficient r: (2,6) (3,0) (5,15) (5,5) (10,2). Give the value to 3 significant digits.

Scatter diagram and correlation coefficient

Below are the gestation days and longevity for 22 animals. a) Make a scatter chart. b) Calculate correlation coefficient and interpret it. c)Test the correlation coefficient for signficance. Clearly stating the degrees of freedom. Animal Gestation (Days) Longevity (Years) Ass 365 12

Correlation, Causation, Independent & Dependent Variables

1. Does correlation equal causation? Does the strength of correlation depend on the direction? What is the meaning of a zero correlation? Explain your answers. 2. What is the difference between an independent and a dependent variable? Does a regression model imply causation? Why or why not? 3. How can you use correlation

Coefficient of correlation and coefficient of determination..

In your own words, describe the concept of correlation, include the coefficient of correlation (r) and the coefficient of determination (r2) in your description. Please include an example data set in your explanation. Again, Excel and MegaStat will do all the necessary calculations. Excel 2003: Tools > Data Analysis > Corre

Positive Correlations (Research Methods)

There is a high positive correlation (0.74) between the eating of green Jello and development of cancer. What does this correlation mean? What is a possible third variable that could explain this correlation?

Making Scatter Diagrams

I need to make a perfect positive linear correlation scatter diagram. Could you please outline this procedure so that I can continue to make other scatter diagrams (if that is possible) like a large but not perfect positive linear correlation, no correlation, large but not perfect negative linear correlation, small positive lin

Test of hypothesis for correlation coefficient

Ten pairs of points yielded a correlation coefficient y of 0.79. If a=0.05, which of the following statements is correct if H 0:P=0? (Do not calculate a t-value.) Because 0.79 is greater than 0.632, the null hypothesis is rejected. Because 0.79 is greater than 0.602, the null hypothesis is not rejected. There is no corr

Women in workforce scatterplot

If you were to draw a scatter plot of the number of women in the workforce versus the number of Christmas trees sold in the United States for each year between 1930 and the present, you would find a very strong correlation. Why do you think this would be true? Does one cause the other?

Scatterplots Correlation for Data Analysis

Use the following situation to answer questions 14 to 18 below: A meteorologist wants to see if there is a relationship between the number of toronados that occur each year and the number of deaths attributed to the tornadoes. The data are shown for 10 recent years. The number of tornados is represented by x, and the numb

Correlation coefficient

Please see the attached file. 10. An agronomy study was performed to compare the yield (in kg/ha) of Sundance winter wheat and Manitou spring wheat under the same conditions. Listed below are actual yields of both varieties of wheat from nine test plot locations. Using a 5% significance level, is there statistically suffici