Statistics key terms

A boundary beyond which a sample result needs checking by taking another sample immediately. For sample means, warning limits are set at two standard deviations of the sample means above and below the expected value.

A relationship in which there is an overall trend, but the points are widely scattered around it.

A number indicating how much influence a value or category has in a calculation, such as its frequency or share of spending.

An index that accounts for the relative importance of different items rather than treating them equally.

An average in which values contribute according to their weights: $\bar{x}_w=\frac{\sum wx}{\sum w}$.

The value of y where a line crosses the y-axis, when $x=0$; for $y=a+bx$, the y-intercept is a.

No apparent increasing or decreasing relationship between two numerical variables.