1. What is the difference between R2 and adjusted R2?

R2 is a statistic that will give some information about the goodness of fit of a model. In regression, the R2 coefficient of determination is a statistical measure of how well the regression line approximates the real data points. An R2 of 1.0 indicates that the regression line perfectly fits the data. Adjusted R2 is a modification of R2 that adjusts for the number of explanatory terms in a model. Unlike R2, the adjusted R2 increases only if the new term improves the model more than would be expected by chance. The adjusted R2 can be negative, and will always be less than or equal to R2. Adjusted R2 does not have the same interpretation as R2. As such, care must be taken in interpreting and reporting this statistic. Adjusted R2 is particularly useful in the Feature selection stage of model building. Adjusted R2 is not always better than R2: adjusted R2 will be more useful only if the R2 is calculated based on a sample, not the entire population. For example, if our unit of analysis is a state, and we have data for all counties, then adjusted R2 will not yield any more useful information than R2.

2. How does testing the significance of the entire multiple regression models differ from testing the contribution of each independent variable?

When testing the significance of the entire multiple regression, we are testing the jointly affect of the regressors (predictors) all together. On the other hand, when testing the contribution of each independent variable, we are testing the affect of that specific variable on the dependent variable.

3. Why and how do you use dummy variables?

The use of dummy variables allows you to include categorical independent variables as

part of the regression model. If a given categorical independent variable has two categories, then you need only one dummy variable to represent the two categories.

...QUESTION 21
The finishing process on new furniture leaves slight blemishes. The table below displays a manager's probability assessment of the number of blemishes on one piece of new furniture.
Number of Blemishes
0
1
2
3
4
5
Probability
0.34
0.25
0.19
0.11
0.07
0.04
1. On average, how many blemishes do we expect on one piece of new furniture?
2. What is the variance of blemishes on one piece of new furniture? (round to the nearest hundredth) ...

...Practice Problems 1-KEY 1. The closing stock price of Ahmadi, Inc. for a sample of 10 trading days is shown below. Day Stock Price 1 84 2 87 3 84 4 88 5 85 6 90 7 91 8 83 9 82 10 86
For the above sample, compute the following measures. a. b. c. The mean = ∑X/n = 860/10 = 86 The median = (85+86)/2 = 85.5 The variance = ∑ X - X 2/ n-1 = {(84-86)2 + (87-86)2 + (84-86)2 + (88-86)2 + (85-86)2 + (90-86)2 + (91-86)2 + (83The standard deviation = √8.89 = 2.98 The coefficient of variation = 2.98/86...

...Air Force Assignment
1. Use appropriate descriptive statistics to summarize the training time data for each method. What similarities or differences do you observe from the sample data?
Descriptive analysis in excel has been used to come up with relevant figures of the given data samples which is tabulated below:
Descriptive Statistics | Current | Proposed |
Mean | 75.06557 | 75.42623 |
Standard Error | 0.505094 | 0.32091 |
Median | 76 |...

...Elementary Statistics Chapter 1 Test - Form A
Name:___________________________ Course Number: __________ Section Number: _____
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
Provide an appropriate response.
1) Define the terms population, sample, parameter and statistic. How does a census compare to a
sample?
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or...

...procedure. (c) Are the target population and sampled population the same? Explain some related problems. (d) Give two variable of interest related to element of the population (one quantitative, the other qualitative). (e) Describe an appropriate method of data collection in this study. Solutions: [5](a) All shoppers at the chain store. More accurate definition would be: All shoppers that regularly shop at the chain store, but then it should require to defining who is a “regular...

...Test 4A AP Statistics Name:
Directions: Do all of your work on these sheets.
Part 1: Multiple Choice. Circle the letter corresponding to the best answer.
1. I measure a response variable Y at each of several times. A scatterplot of log Y versus time of measurement looks approximately like a positively sloping straight line. We may conclude that
(a) the correlation between time of measurement and Y is negative, since logarithms of positive fractions (such as...

...the written application of operation. It teaches students to think clearly, reason well and strategize effectively. Mental Mathematics is the ability to utilise mathematical skills to solve problems mentally. The marks scored by pupils generate statistics which are used by teachers to analyse a student’s performance and development of theories to explain the differences in performance.
The Standard 3 class is where the transition from junior to senior level occurs where...

...Steps in the Quantitative Research Process?
Problem statement(s) + background Purpose of the research Aims/objectives of the research Research question(s) Research hypothesis or hypotheses Review of the literature (ROL) Conceptual, theoretical framework
Steps in the Research Process (cont.)
Design & Methodology, Sampling Collection of Data: Methods, measurements, assessment Analysis & Interpretation of Data Research dissemination & utilization
1
The...

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