Applied Business Tools ECO 6416 Assessing Validity
Validity of Studies Based on Multiple Regression
Step back and take a broader look at regression: Is there a systematic way to assess/critique regression studies?
strengths and pitfalls?
ECO 6416 - Dr. Dickie - Exercise - Normal Distribution
Normal Distribution Tables required for this exercise
Problem 1. Scores on a recent national statistics exam were normally distributed with a mean of 80 and a standard deviation of 6. a. b. c. What is
Multiple Regression and Correlation
Multiple regression analysis is the study of how a dependent variable y is related to two or more independent variables. In
the general case, we will use p to denote the number of i
Bayesian Statistical Inference: An Introduction Statistical inference describes the procedures by which we use the observed data to draw conclusions about the population from which the data came or about the process by which the data were generated. Our a
Regression Modeling Selection Process
When you have more than one regression equation based on data, to select the
best model", you should compare:
1. R-squares: That is, the percentage of variance [in fact, the sum of squares] in Y accounted
for by varia
Chi-square Density Function The probability density curve of a Chi-square distribution is an asymmetric curve stretching over the positive side of the line and having a long right tail. The form of the curve depends on the value of a parameter known as th
Multinomial Probability Function A multinomial random variable is an extended binomial. However, the difference is that in a multinomial case, there are more than two possible outcomes. There are a fixed number of independent outcomes, with a given probab
Normal Density Function In the Descriptive Statistic Section of this Web site, we have been concerned with how empirical scores are distributed and how best to describe their distribution. We have discussed several different measures, but the mean will be
Poisson Probability Function Life is good for only two things, discovering mathematics and teaching mathematics. - Simeon Poisson An important class of decision problems under uncertainty is characterized by the small chance of the occurrence of a particu
Blending the Classical and the P-value Based Approaches in Test of Hypotheses A p-value is a measure of how much evidence you have against the null hypothesis. Notice that the null hypothesis is always in = form, and does not contain any forms of inequali
Parametric vs. Non-Parametric vs. Distribution-free Tests One must use a statistical technique called non-parametric if it satisfies at least one of the following five types of criteria: 1. The data entering the analysis are enumerative; that is, counted
Test for Equality of Several Population Medians Generally, the median provides a better measure of location than the mean when there are some extremely large or small observations; i.e., when the data are skewed to the right or to the left. For this reaso
Chapter 10: Multiple Regression Practice Exam
You have 20 minutes to complete the 10 Multiple Regression practice questions.
1. The Owner of Showtime Movie Theaters, Inc., would like to
Simple Linear Regression
Chapter 9 Regression and Correlation Analysis
Regression analysis uses an equation (regression equation) to express the relationship between one continuous
quantitative characteristic of a population (dependent variable) and one (
Chapter 9: Simple Linear Regression Practice Exam
You have 20 minutes to complete the 10 simple linear regression practice questions.
1. Define the variables used in simple linear regre
Seasonal Index and Deseasonalizing Data
Seasonal index represents the extent of seasonal influence for a particular segment of the year.
The calculation involves a comparison of the expected values of that period to the grand mean.
We need to get an estim
Distribution-free Equality of Two Populations For statistical equality of two populations, one may use the Kolmogorov-Smirnov Test (K-S Test) for two populations. The K-S test seeks differences between the two population's distribution function based on t
2 by 2 Crosstable Analysis Using Chi-square in a 2x2 table requires the Yates's correction. One first subtracts 0.5 from the absolute differences between observed and expected frequencies for each of the three genotypes before squaring, dividing by the ex
Goodness-of-Fit Test for Probability Mass Functions There are other tests that might use the Chi-square, such as goodness-of-fit test for discrete random variables. Therefore, Chi-square is a statistical test that measures "goodness-of-fit". In other word
Student T-Density Function The t distributions were discovered in 1908 by William Gosset, who was a chemist and a statistician employed by the Guinness brewing company. He considered himself a student still learning statistics, so that is how he signed hi
Testing the Variance: Is the Quality that Good?
Suppose a population has a normal distribution. The manager is to test a specific
claim made about the quality of the population by way of testing its variance 2.
Among three possible scenarios, the interest
Triangular Density Function The triangular distribution shows the number of successes when you know the minimum, maximum, and most likely values. For example, you could describe the number of intakes seen per week when past intake data show the minimum, m
Managing the Producer's or the Consumer's Risk The logic behind a statistical test of hypothesis is similar to the following logic. Draw two lines on a paper and determine whether they are of different lengths. You compare them and say, "Well, certainly t
Pearson, Spearman, and Point-Biserial Correlations
There are measures that describe the degree to which two variables are linearly related. For the
majority of these measures, the correlation is expressed as a coefficient that ranges from 1.00 to
Test for Normality The standard test for normality is the Lilliefors' statistic. A histogram and normal probability plot will also help you distinguish between a systematic departure from normality when it shows up as a curve. Lilliefors' Test for Normali
Hypothesis Testing: Rejecting a Claim To perform a hypothesis test, one must be very specific about the test one wishes to perform. The null hypothesis must be clearly stated, and the data must be collected in a repeatable manner. If there is any subjecti
Correlation, and Level of Significance
It is intuitive that with very few data points, a high correlation may not be statistically
significant. You may see statements such as, correlation is significant between x and y at the
= 0.005 level" and correlati
Introduction to Estimation To estimate means to esteem (to give value to). An estimator is any quantity calculated from the sample data which is used to give information about an unknown quantity in the population. For example, the sample mean is an estim
Revising the Expected Value and the Variance Averaging Variances: What is the mean variance of k variances without regard to differences in their sample sizes? The answer is simply: Average of Variances = [Si2] / k However, what is the variance of all k g