If events A and B are independent, what is the P(A ∩ B)?
- P(A) * P(B)
- P(A) + P(B)
- P(A) - P(B)
- P(A) / P(B)
If events A and B are independent, the probability of both events occurring (P(A ∩ B)) is the product of their individual probabilities (P(A) * P(B)). This is a direct result of the Multiplication Rule for independent events.
What are the degrees of freedom in a Chi-square test for goodness of fit?
- The number of categories minus 1
- The number of categories plus 1
- The number of observations minus 1
- The number of observations plus 1
In a Chi-square test for goodness of fit, the degrees of freedom are calculated as the number of categories minus 1.
What does inference in multiple linear regression primarily involve?
- Calculating the mean of the residuals
- Creating the scatter plot
- Drawing the best fit line
- Interpreting the coefficients
Inference in multiple linear regression primarily involves interpreting the coefficients of the model, which represent the expected change in the response variable for each one-unit change in the respective explanatory variable, assuming all other variables are held constant.
What does kurtosis measure in a dataset?
- Central tendency
- Dispersion
- Skewness
- The "tailedness" of the distribution
Kurtosis is a statistical measure that defines how heavily the tails of a distribution differ from the tails of a normal distribution. In other words, kurtosis identifies whether the tails of a given distribution contain extreme values.
How is the variance related to the standard deviation in a data set?
- The variance is the average of the standard deviation
- The variance is the square of the standard deviation
- The variance is the square root of the standard deviation
- The variance is twice the standard deviation
The variance is the square of the standard deviation. Standard deviation is a measure of dispersion in a dataset and variance is a square of it, meaning that they both represent the same concept of dispersion, but in different units.
What is the assumption made when computing the Pearson correlation coefficient?
- The correlation is zero
- The variables are independent
- The variables are normally distributed
- There is a linear relationship between variables
When computing the Pearson correlation coefficient, it is assumed that there is a linear relationship between the variables. Furthermore, it's also assumed that the variables are continuous and that the data is homoscedastic (i.e., the variance of the errors is the same across all levels of the variables).
Conditional independence of A and B given C means that knowing that C has occurred does not change the ________ between A and B.
- Difference
- Intersection
- Ratio
- Relationship
Conditional independence of A and B given C means that knowing that C has occurred does not change the relationship between A and B. In other words, the occurrence of event C does not affect the independence of events A and B.
What is the purpose of 'normalization' or 'standardization' in the pre-processing step of cluster analysis?
- To decrease the number of clusters
- To ensure that all features contribute equally to the distance calculation
- To handle missing values
- To increase the computational complexity
Normalization or standardization ensures that all features contribute equally to the final distance calculation, regardless of their original scale. Without this step, features with larger scales would dominate the distance calculation, potentially leading to misleading clusters.
How does the height of a bar in a histogram relate to the frequency of the data?
- It has no relation with the frequency
- It represents the cumulative frequency
- It represents the mean frequency
- It represents the relative frequency
The height of a bar in a histogram represents the frequency (or relative frequency) of data for that particular bin. This means the taller the bar, the more data falls into that specific interval.
A statistical test has more power to detect an effect if the effect size is ______.
- Equal to the sample size
- Large
- Small
- Unchanged
The power of a test is influenced by the effect size - the magnitude of the difference or relationship you're testing for. Larger effect sizes increase the power of a test because they create a larger signal relative to the noise, making it easier to detect an effect if one exists.
In what kind of scenario is the Central Limit Theorem used?
- It's used only when dealing with a uniform distribution.
- It's used to determine whether an event will occur.
- It's used to predict the future.
- It's used when we want to make inferences about a population based on a sample.
The Central Limit Theorem (CLT) is often used in scenarios where we are interested in the average outcome of a large number of independent or nearly independent events. This is commonly the case when we are making inferences about a population based on a sample.
How does the Central Limit Theorem relate to the use of Z-tests?
- It allows for the assumption that the sample mean distribution is normally distributed
- It enables the calculation of the sample standard deviation
- It increases the power of the test
- It reduces the impact of outliers in the sample
The Central Limit Theorem states that, with a large enough sample size, the distribution of the sample mean will be approximately normally distributed. This allows us to use Z-tests even when the population is not normally distributed.