How to perform Heteroscedasticity test in STATA for time series data
Heteroskedastic means “differing variance” which comes from the Greek word “hetero” (‘different’) and “skedasis” (‘dispersion’). It refers to the variance of the error terms in a regression model in an independent variable. If heteroscedasticity is present in the data, the variance differs across the values of the explanatory variables and violates the assumption. This will […]
How to test time series autocorrelation in STATA
This article shows a testing serial correlation of errors or time series autocorrelation in STATA. An autocorrelation problem arises when error terms in a regression model correlate over time or are dependent on each other. Why test for autocorrelation? It is one of the main assumptions of the OLS estimator according to the Gauss-Markov theorem that in […]
How to test time series autocorrelation in STATA?
Why test for autocorrelation? It is one of the main assumptions of the OLS estimator according to the Gauss-Markov theorem that in a regression model: Cov(ϵ_(i,) ϵ_j )=0 ∀i,j,i≠j, where Cov is the covariance and ϵ is the residual. The presence of autocorrelation in the data causes and correlates with each other and violates the assumption, showing bias in the […]
How to Find Degrees of Freedom | Definition & Formula
Degrees of freedom, often represented by v or df, is the number of independent pieces of information used to calculate a statistic. It’s calculated as the sample size minus the number of restrictions. Degrees of freedom are normally reported in brackets beside the test statistic, alongside the results of the statistical test. Example: Degrees of freedomSuppose you randomly sample […]
How to Write a Thesis Statement
How to Write a Thesis Statement What is a Thesis Statement? Almost all of us—even if we don’t do it consciously—look early in an essay for a one- or two-sentence condensation of the argument or analysis that is to follow. We refer to that condensation as a thesis statement. Why Should Your Essay Contain a […]
Unbiased Sampling Techniques – random, systematic, stratified, and cluster sampling.
To obtain samples that are unbiased—i.e., that give each subject in the population an equally likely chance of being selected—statisticians use four basic methods of sampling: random, systematic, stratified, and cluster sampling. Random Sampling Random samples are selected by using chance methods or random numbers. One such method is to number each subject in […]
When to use the chi-square goodness of fit test – tables, formulas and examples
The chi-square goodness of fit test is a statistical test used to determine whether there is a significant difference between the expected and observed frequencies in one or more categories. It is often applied when dealing with categorical data and is useful for assessing whether the distribution of observed categorical data differs from a theoretical […]
How to Write an Argumentative Essay: Examples & Tips
How to Write an Argumentative Essay: Examples & Tips Writing an argumentative essay involves presenting a well-supported argument in favor of a particular thesis statement. Whether you encounter this task in high school or at the university level, mastering the art of argumentation is crucial. This article provides a guide on how to write an […]
Exploratory Factor Analysis (EFA) Results Interpretation
Exploratory Factor Analysis (EFA) Results Interpretation Appropriateness of data (adequacy) KMO Statistics Marvelous: .90s Meritorious: .80s Middling: .70s Mediocre: .60s Miserable: .50s Unacceptable: <.50 Bartlett’s Test of Sphericity Tests hypothesis that correlation matrix is an identity matrix. Diagonals are ones Off-diagonals are zeros A significant result (Sig. < 0.05) indicates matrix is not an identity […]
Factoring Methods in Exploratory Factor Analysis (EFA)
Factoring Methods in Exploratory Factor Analysis (EFA) There are three main methods for factor extraction. Principal Component Analysis (PCA) Use for a softer solution Considers all of the available variance (common + unique) (places 1’s on diagonal of correlation matrix). Seeks a linear combination of variables such that maximum variance is extracted—repeats this step. Use when […]
