Stats Review

The purpose of correlation analysis is to find how strong the relationship is between 2 variables

• A.

  True

• B.

  False

A correlation coefficient of -1 or +1 indicates perfect correlation

• A.

  True

• B.

  False

The strength of the correlation btwn 2 variables depends on the sign of the coefficient of correlation

• A.

  True

• B.

  False

A coefficient of correlation r close to 0 (say 0.08) shows that the relationship btwn 2 variables is quite weak

• A.

  True

• B.

  False

Coefficients of -0.91 and +0.91 have equal strength

• A.

  True

• B.

  False

If a scatter diagram shows very little scatter about a straight line drawn through the plots, it indicates a rather weak relationship

• A.

  True

• B.

  False

The coefficient of determination is found by taking the square root of the coefficient of correlation

• A.

  True

• B.

  False

If the coefficient of correlation is -0.9, the coefficient of determination is -0.81

• A.

  True

• B.

  False

The coefficient of determination can only be positive

• A.

  True

• B.

  False

In order to visualize the form of the regression equation, we can draw a scatter diagram

• A.

  True

• B.

  False

A line found using the least squares principle is the best-fitting line because the sum of the squares of the vertical deviations btwn the actual and estimated values is minimized

• A.

  True

• B.

  False

The regression equation is used to estimate a value of the dependent variable y based on a selected value of the independent variable x

• A.

  True

• B.

  False

In regression analysis, the predicted value of y' rarely agrees exactly with the actual y value, i.e. we expect some prediction error

• A.

  True

• B.

  False

An economist is interested in predicting the unemployment rate based on gross domestic product. since the economist is interested in predicting unemployment, the independent variable is gross domestic product

• A.

  True

• B.

  False

If we are studying the relationship btwn high school performance and college performance, and want to predict college performance, high school performance is the indy or dependy variable?

What is the range of values that the coefficient of determination can assume? __ and ___

A financial advisor is interested in predicting bond yield based on bond term, ie 1 yr, 2yrs, etc. what is the dependent variable?

If the value of r is -.96, what does this indicate about the dependent variable as the independent variable increases

Perfect correlation means that the scatter diagram will appear as a ______

If the correlation btwn sales and advertising is 0.6, what percent of the variation in sales can be measured?

If the dependent variable is measured in dollars, in what units is the standard error of estimate measured?

The following table shows the number of workdays absent based on the length of employment in years# of workdays absent     2     3     3     5     7     7     8length of emplmnt (yrs)   5     6     9     4     2     2     0What is the independent variable (x)?

The following table shows the number of workdays absent based on the length of employment in years# of workdays absent     2     3     3     5     7     7     8length of emplmnt (yrs)   5     6     9     4     2     2     0what is the dependent variable (y)?

The following table shows the number of workdays absent based on the length of employment in years# of workdays absent     2     3     3     5     7     7     8length of emplmnt (yrs)   5     6     9     4     2     2     0what is the slope of the linear equation?

The following table shows the number of workdays absent based on the length of employment in years# of workdays absent     2     3     3     5     7     7     8length of emplmnt (yrs)   5     6     9     4     2     2     0what is the y intercept of the linear equation?

The following table shows the number of workdays absent based on the length of employment in years# of workdays absent     2     3     3     5     7     7     8length of emplmnt (yrs)   5     6     9     4     2     2     0what is the least squares equation for the data?

What is the standard error of estimate?

The relationship btwn interest rates as a percent (x) and housing starts (y) is given by the linear equation y'=4094-269xwhat will be the # of housing starts if the interest rate is 8.25%?

The relationship btwn interest rates as a percent (x) and housing starts (y) is given by the linear equation y'=4094-269xat what interest rate will there be no permits for housing starts?

The relationship btwn interest rates as a percent (x) and housing starts (y) is given by the linear equation y'=4094-269xwhat happens to housing starts as interest rates fall?

Which of the following statements regarding the coefficient of correlation is true?

• A.

  It ranges from -1 to +1 inclusive

• B.

  It measures the strength of the relationship btwn 2 variables

• C.

  A value of 0 indicates 2 variables are not related

• D.

  All of the above

• E.

  None of the above

What does a coefficient of correlation of .7 infer?

• A.

  Almost no correlation because .7 is close to 1

• B.

  70% of the variation in one variable is explained by the other

• C.

  Coefficient of determination is 0.49

• D.

  Coefficient of nondetermination is .3

• E.

  None of the above

If the correlation btwn 2 variables is close to one, the association is 

• A.

  Strong

• B.

  Moderate

• C.

  Weak

• D.

  None

If the correlation coefficient btwn 2 variables = 0, what can be said of the variables x and y?

• A.

  Not related

• B.

  Dependent on each other

• C.

  Highly related

• D.

  All of the above are correct

• E.

  None of the above are correct

Which value of r indicates a stronger correlation than .4?

• A.

  -.3

• B.

  -.5

• C.

  .38

• D.

  0

• E.

  None of the above

Which value of r indicates a stronger correlation than -.4?

• A.

  -.3

• B.

  -.5

• C.

  0

• D.

  .3

• E.

  None of the above

Which value of r indicates a stronger correlation than .25?

• A.

  -.3

• B.

  -.5

• C.

  .3

• D.

  All of the above

• E.

  None of the above

In the regression equation, y'=a + bx, what does the letter a represent?

• A.

  Y intercept

• B.

  Slope

• C.

  Any value of the independent variable that is selected

• D.

  None of the above

In the regression equation, y'=a + bx, what does the letter b represent?

• A.

  Y intercept

• B.

  Slope

• C.

  Any value of the independent variable that is selected

• D.

  Value of y when x=0

• E.

  None of the above

If all the plots on a scatter diagram lie on a straight line, what is the standard error of estimate

• A.

  -1

• B.

  1

• C.

  0

• D.

  Infinity

• E.

  None

Which of the following is true about the standard error of estimate

• A.

  Measure the accuracy of the prediction

• B.

  Based on squared vertical deviations between y and y'

• C.

  Cant be negative

• D.

  All

• E.

  None

Given the following five pts: (-2, 0), (-1, 0), (0,1), (1,1) and (2,3)what is the slope of the line?

• A.

  0

• B.

  .5

• C.

  .6

• D.

  .7

• E.

  None

Given the following five pts: (-2, 0), (-1, 0), (0,1), (1,1) and (2,3)what is the y intercept

• A.

  0

• B.

  .7

• C.

  1

• D.

  1.5

• E.

  None

What is the standard error of the estimate?

• A.

  0

• B.

  .135

• C.

  .367

• D.

  .606

• E.

  None

A commuter travels many miles to work each morning. she has timed this trip 5 times during the last month.  the time (in min) required to make this trip was 44, 39, 41, 35, and 41. the mean time required for this trip was 40 min.  what is the variance for this sample data?

• A.

  8.8

• B.

  11

• C.

  0

• D.

  3

• E.

  -2

Which of the following is not a legitimate probability value?

• A.

  .67

• B.

  15/16

• C.

  .23

• D.

  2/3

• E.

  -.28

Consider the relative frequency distribution given belowclass interval relative frequency20 under 40 .240 under 60 .360 under 80 .480 under100 .1

• A.

  90

• B.

  80

• C.

  .9

• D.

  54

• E.

  100

Consider the following stem and leaf plotstem leaf1 0,2,5,72 2,3,4,83 0,4,6,6,94 5,8,8,95 2,7,8suppose that a frequency distribution was developed from this, and there were 5 classes (10 under 20, 20 under 30, etc) what is the cumulative frequency for the 30 under 40 class interval?

• A.

  5

• B.

  9

• C.

  13

• D.

  14

• E.

  18

The number of phone calls arriving at a switchboard each hr has been recorded, and the following frequency distribution has been developedclass interval frequency20 under 40 3040 under 60 45 60 under 80 8080 under 100 45what is the cumulative frequency of the third class?

• A.

  80

• B.

  .4

• C.

  155

• D.

  75

• E.

  105

The mean life of a particular brand of light bulb is 1000 hrs and the standard deviation is 50 hrs. we can conclude that at least 75% of this brand of bulbs will last between

• A.

  900 and 1100 hrs

• B.

  950 and 1050

• C.

  850 and 1150

• D.

  800 and 1200

• E.

  1050 and 1250