Statistics Exam Two

What is a variable in statistics?

A characteristic measured on a subject, which can be quantitative or categorical.

What is measurement error?

The difference between the measured value and the true value, which can be systematic or random.

Define bias in measurement.

Systematic over- or under-measurement that affects accuracy.

What does precision refer to in measurements?

How consistent repeated measurements are, regardless of bias.

What is random error?

Unpredictable variation in measurements that can be reduced by averaging.

How do you calculate range?

Range = maximum value - minimum value.

What is standard deviation (SD)?

A measure that describes the typical distance of data points from the mean.

What does validity mean in measurement?

A measure is valid when it accurately measures the variable or construct it is intended to measure.

What is sensitivity in test performance?

The proportion of actual positives correctly identified, calculated as TP/(TP + FN).

What is specificity in test performance?

The proportion of actual negatives correctly identified, calculated as TN/(TN + FP).

What is a pie chart used for?

To represent categorical data where categories are mutually exclusive and proportions sum to 1.

What is a bar graph?

A graph that displays categorical data with categories on the x-axis and counts or proportions on the y-axis.

What is a time-series plot?

A graph that shows data points in time order, useful for identifying trends and patterns.

What is a histogram?

A graphical representation of the distribution of numerical data using bins for intervals on the x-axis.

What is a stem-and-leaf plot?

A plot that displays quantitative data while preserving the original values, useful for small datasets.

What is the five-number summary?

A summary that includes the minimum, Q1, median, Q3, and maximum of a dataset.

What does IQR stand for?

Interquartile Range, calculated as Q3 - Q1, representing the spread of the middle 50% of data.

What is a boxplot?

A graphical representation that summarizes data using the five-number summary and identifies outliers.

What is a normal distribution?

A symmetric, bell-shaped distribution characterized by its mean and standard deviation.

What is the Empirical Rule?

In a normal distribution, approximately 68% of data falls within 1 SD, 95% within 2 SDs, and 99.7% within 3 SDs.

What is a z-score?

A measure that indicates how many standard deviations an observation is from the mean.

What does the Law of Large Numbers state?

As the number of trials increases, sample results tend to settle near the expected long-run pattern.

How do you calculate the number of possible sequences in trials?

By raising the number of outcomes per trial to the power of the number of trials.

What is the formula for calculating sensitivity?

Sensitivity = TP / (TP + FN).

What is the formula for calculating specificity?

Specificity = TN / (TN + FP).

What does the 1.5 × IQR rule help identify?

It helps identify outliers in a dataset.

What does a right-skewed distribution indicate about the mean and median?

In a right-skewed distribution, the mean is greater than the median.

What is the upper outlier fence formula?

Upper fence = Q3 + 1.5(IQR).

What is the z-score for an observation of 80 if the mean is 70 and SD is 5?

z = (80 - 70) / 5 = 2.