What is the significance of the total probability rule?
- It is a rule for determining the probability of dependent events
- It is used to calculate conditional probabilities
- It is used to calculate the probability of mutually exclusive events
- It provides a way to break down probabilities of complex events into simpler ones
The Total Probability Rule provides a way to compute the probability of an event from the probabilities of that event occurring within disjoint subsets of the sample space. It essentially allows you to break down the probability of complex events into simpler or more basic component events.
In a Chi-square test for goodness of fit, the degrees of freedom are calculated as the number of categories minus ________.
- one
- the number of samples
- three
- two
In a Chi-square test for goodness of fit, the degrees of freedom are calculated as the number of categories minus one. This reflects the number of values in the final calculation that are free to vary.
How does bin size affect a histogram representation?
- Bin size changes the shape of the histogram
- Bin size does not affect the histogram
- Larger bins make the histogram more detailed
- Smaller bins make the histogram more detailed
The choice of bin size in a histogram can greatly affect the resulting visualization. If the bins are too large, important features of the data may be obscured. If the bins are too small, the histogram may appear too 'noisy' and it may be difficult to interpret underlying patterns. Thus, the choice of bin size can indeed change the perceived shape of the histogram.
How can the problem of heteroscedasticity be resolved in linear regression?
- By adding more predictors
- By changing the estimation method
- By collecting more data
- By transforming the dependent variable
Heteroscedasticity can be resolved by transforming the dependent variable, typically using a logarithmic transformation. This often stabilizes the variance of the residuals across different levels of the predictors.
When is a Poisson distribution used?
- When each event is dependent on the previous event
- When the events are independent and occur at a constant rate
- When the events are normally distributed
- When the events have only two possible outcomes
A Poisson distribution is used when we are counting the number of times an event happens over a fixed interval of time or space, and the events are independent and occur at a constant average rate. It's often used to model random events such as calls to a call center or arrivals at a website.
How can qualitative data be transformed into quantitative data for analysis?
- By calculating the mean
- By coding the responses
- By conducting a t-test
- This transformation is not possible
Qualitative data can be transformed into quantitative data for analysis by coding the responses. This is a process where categories or themes identified in the qualitative data are assigned numerical codes. These numerical codes can then be used in statistical analyses. For instance, if you have data on types of pets (dogs, cats, etc.), you can assign a numerical code (1 for dogs, 2 for cats, etc.) to transform this qualitative data into quantitative data.
What does it mean when we say that a distribution is skewed?
- All data points are identical
- It has outliers
- It is not symmetric about its mean
- Its mean and median are not equal
When we say that a distribution is skewed, we mean that the distribution is not symmetric about its mean. In a skewed distribution, the data points are not evenly distributed around the mean, with more data on one side of the mean than the other.
What is multicollinearity and how does it affect simple linear regression?
- It is the correlation between dependent variables and it has no effect on regression
- It is the correlation between errors and it makes the regression model more accurate
- It is the correlation between independent variables and it can cause instability in the regression coefficients
- It is the correlation between residuals and it causes bias in the regression coefficients
Multicollinearity refers to a high correlation among independent variables in a regression model. It does not reduce the predictive power or reliability of the model as a whole, but it can cause instability in the estimation of individual regression coefficients, making them difficult to interpret.
The distribution of all possible sample means is known as a __________.
- Normal Distribution
- Population Distribution
- Sampling Distribution
- Uniform Distribution
The sampling distribution in statistics is the probability distribution of a given statistic based on a random sample. For a statistic that is calculated from a sample, each different sample could (and likely will) provide a different value of that statistic. The sampling distribution shows us how those calculated statistics would be distributed.
How is 'K-means' clustering different from 'hierarchical' clustering?
- Hierarchical clustering creates a hierarchy of clusters, while K-means does not
- Hierarchical clustering uses centroids, while K-means does not
- K-means requires the number of clusters to be defined beforehand, while hierarchical clustering does not
- K-means uses a distance metric to group instances, while hierarchical clustering does not
K-means clustering requires the number of clusters to be defined beforehand, while hierarchical clustering does not. Hierarchical clustering forms a dendrogram from which the user can choose the number of clusters based on the problem requirements.