# Statistics: Modeling the World (Chapter 6 Terms/Vocabulary)

## 13 terms

### Shifting

Adding a constant to each data value adds the same constant to the mean, the median and the quartiles, but does not change the standard deviation or IQR.

### Rescaling

Multiplying each data value by a constant multiplies both the measures of position (mean, median and quartiles) and the measures of spread (standard deviation and IQR) by that constant.

### Standardizing

We standardize to eliminate units. Standardized values can be compared and combined even if the original variables had different units and magnitudes.

### Standardized Value

A value found by subtracting the mean and dividing by the standard deviation.

### Normal Model

A useful family of models for unimodal, symmetric distributions.

### Parameter

A numerically value attribute of a model. For example, the values of mean and standard deviation in a Normal Model are parameters.

### Statistic

A value calculated from data to summarize aspects of the data. For example, the mean and standard deviation are statistics.

### z-score

Tells how many standard deviations a value is from the mean; have a mean of zero and a standard deviation of one.

### Standard Normal Model

A Normal Model with mean = 0 and standard deviation = 1.

### 68-95-99.7 Rule

68% fall within 1 SD from the mean, 95% fall within 2 SD's from the mean, 99.7% fall within 3 SD's from the mean.

### Normal Percentile

Corresponds to the z-score giving the percentage of values in a standard Normal distribution found at that z-score or below.

### Normal Probability Plot

A display to help assess whether a distribution of data is approximately Normal. If the plot is nearly straight, the data satisfy the Nearly Normal Condition.