Math 146-Wurts/ Chapter 6-Putting statistics to work

margin of error

1/square root of n

Box Plot (Box and Whisker Plot)

Shows distribution of data values on a number line. Divided into quartiles.

Quartiles

Values that divide a data set into four equal parts Low value lower value median-middle upper quartile high value

standard deviation

A measure of variability that describes an average distance of every score from the mean. Add all values. Divide the total by the number of data values -1. Example: If you have 8 value numbers present, divide by 7.

confidence interval

A range of values so defined that there is a specified probability that the value of a parameter lies within it.

statiscally significant

A set of measurements or observations in a statistical study that if it is unlikely to have occurred by chance.

Distribution

A variable (or data set) refers to the way its values are spread over all possible values. A distribution can be shown visually with a table or graph.

Variation

How widely data values are spread out about the center of a distribution.

68-95-99.7 rule

In a normal model, about 68% of values fall within 1 standard deviation of the mean, about 95% fall within 2 standard deviations of the mean, and about 99.7% fall within 3 standard deviations of the mean.

Outliner

Is a data value that is much higher or much lower than almost all other values. The outliner can change the mean of a data set but does not affect the median or mode.

Mean

Most commonly call the average value. Mean = Add all numbers, then divide by total numbers of values.

Standard scores and percentiles

Percentage of scores that fall below a point on a score distribution; for example, a score at the 75th percentile indicates that 75% of students obtained that score or lower.

five number summary

minimum, 1st quartile, median, 3rd quartile, maximum

Shapes of Distributions

symmetric, skewed right, skewed left

Mode

The value that occurs most frequently in a given data set.

symmetric distribution

Data that are evenly distributed.

Multimodal

Describes a graph of quantitative data with more than two clear peaks.

Range

Distance between highest and lowest scores in a set of data. Take highest value minus the lowest value.

range rule of thumb

Dividing the range by 4, given an approximation of the standard deviation.

standard score (z-score)

Refers to how many standard deviations away from the mean a particular score is located.

lower quartile

The median of the lower half of a set of data.

upper quartile

The median of the upper half of a set of data.

middle quartile

The median or 50th percentile.

Median

The middle value in the sorted data set, or halfway between the two values if the number of values is even.

skewed right distribution

The peak of the data is to the left side of the graph. There are only a few data points to the right side of the graph.

Skewed Left Distribution

The peak of the data is to the right side of the graph. There are only a few data points to the left side of the graph.