Q-Q plot is defined as:

Q-Q plot is defined as:

• A. A plot comparing observed and expected frequencies.
• B. A plot of residuals versus fitted values.
• C. A histogram of data quantiles.
• D. Short for quantile-quantile plot; plots the quantiles of a variable against the quantiles of a specified distribution; if points fall on the diagonal, distributions match.

Answer: (D)

A Q-Q plot (quantile-quantile plot) compares the quantiles of your data to the quantiles of a specified theoretical distribution. You map each percentile’s data value to the corresponding percentile in the reference distribution and plot those paired values. If the points align along the diagonal, the data come from a distribution that matches the reference (same shape, spread, and location). Deviations from the diagonal reveal differences, such as heavier or lighter tails or a shift in central tendency. This is especially useful for checking normality by comparing to the normal distribution, but you can use any theoretical distribution as the reference. Other plots described are different diagnostic tools: a residuals-versus-fitted plot is used in regression diagnostics, and a plot of observed versus expected frequencies relates to goodness-of-fit checks. A histogram of data quantiles isn’t how a Q-Q plot is constructed.

A Q-Q plot (quantile-quantile plot) compares the quantiles of your data to the quantiles of a specified theoretical distribution. You map each percentile’s data value to the corresponding percentile in the reference distribution and plot those paired values. If the points align along the diagonal, the data come from a distribution that matches the reference (same shape, spread, and location). Deviations from the diagonal reveal differences, such as heavier or lighter tails or a shift in central tendency. This is especially useful for checking normality by comparing to the normal distribution, but you can use any theoretical distribution as the reference. Other plots described are different diagnostic tools: a residuals-versus-fitted plot is used in regression diagnostics, and a plot of observed versus expected frequencies relates to goodness-of-fit checks. A histogram of data quantiles isn’t how a Q-Q plot is constructed.