When the residuals exhibit a pattern or trend rather than a random scatter, it is a sign of _________.
- Autocorrelation
- Model misspecification
- Overfitting
- Underfitting
When the residuals exhibit a pattern or trend rather than a random scatter, it can be a sign of model misspecification, i.e., the model doesn't properly capture the relationship between the predictors and the outcome variable.
The branch of statistics that involves using a sample to draw conclusions about a population is called ________ statistics.
- descriptive
- inferential
- numerical
- qualitative
Inferential statistics is the branch of statistics that involves using a sample to draw conclusions about a population. It takes data from a sample and makes inferences about the larger population from which the sample was drawn. For example, inferential statistics might use data from a sample of women to infer something about the mean weight of all women.
Under what circumstances can the mode of a data set be irrelevant or misleading?
- When the data is continuous
- When the data set is large
- When the data set is small
- When there are multiple modes
The mode can be misleading or irrelevant especially with continuous data. Since the mode is the most frequently occurring value, with continuous data the frequency of each value is often the same (i.e., 1), hence it becomes difficult to define a mode in a traditional sense.
A Variance Inflation Factor (VIF) greater than 5 indicates a high degree of _______ among the predictors.
- correlation
- distribution
- multicollinearity
- variance
A VIF greater than 5 is often taken as an indication of high multicollinearity among the predictors in a regression model. This could lead to imprecise and unreliable estimates of the regression coefficients.
How does the 'elbow method' help in determining the optimal number of clusters in K-means clustering?
- By calculating the average distance between all pairs of clusters
- By comparing the silhouette scores for different numbers of clusters
- By creating a dendrogram of clusters
- By finding the point in the plot of within-cluster sum of squares where the decrease rate sharply shifts
The elbow method involves plotting the explained variation as a function of the number of clusters and picking the elbow of the curve as the number of clusters to use. This 'elbow' is the point representing the optimal number of clusters at which the within-cluster sum of squares (WCSS) doesn't decrease significantly with each iteration.
The bin width (and thus number of categories or ranges) in a histogram can dramatically affect the ________, skewness, and appearance of the histogram.
- Interpretation
- Mean
- Median
- Mode
The bin width and the number of bins in a histogram can dramatically affect the interpretation, skewness, and overall appearance of the histogram. This is because the choice of bin size can influence the level of detail visible in the histogram, potentially either obscuring or highlighting certain patterns in the data.
In PCA, if two variables are similar, they will have _______ loadings on the same component.
- high
- low
- opposite
- random
In PCA, if two variables are similar or highly correlated, they will have high loadings on the same component. This is because PCA identifies the directions (Principal Components) in which the data varies the most, and similar variables will contribute to this variance in the same way.
What is the impact of heteroscedasticity on a multiple linear regression model?
- It affects the linearity of the model
- It affects the normality of the residuals
- It causes multicollinearity
- It invalidates the statistical inferences that could be made from the model
Heteroscedasticity, or non-constant variance of the error term, can invalidate statistical inferences that could be made from the model because it violates one of the assumptions of multiple linear regression. This could lead to inefficient estimation of the regression coefficients and incorrect standard errors, which in turn affects confidence intervals and hypothesis tests.
What is the impact of data transformation on the decision to use non-parametric tests?
- A suitable data transformation may make it possible to use a parametric test
- Data transformation always leads to non-parametric tests
- Data transformation always makes data normally distributed
- Data transformation does not affect the choice between parametric and non-parametric tests
A suitable data transformation may make it possible to use a parametric test instead of a non-parametric test. Transformations can help to stabilize variances, normalize the data, or linearize relationships between variables, allowing for the use of parametric tests that might have more statistical power.
If two events are independent, what is the conditional probability of one given the other?
- 0
- 1
- Equal to the probability of the given event
- Undefined
If two events are independent, the conditional probability of one event given the other is simply the probability of the event itself. This is because in independent events, the occurrence of one event does not affect the occurrence of the other event.