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Bootstrap confidence interval alt text

Three linked graphs with same axes 170 – 230, marked in tens.

The top graph, labelled *Sample*, is a dot plot of the sample with its mean marked by a blue vertical line at 209.60 and the bootstrap confidence interval shown by a red horizontal line segment. Red downwards arrows show the values of the endpoints of the bootstrap confidence interval (203.56 and 215.52). There is a box plot below the dots: minimum 170, lower quartile 197, median 208, upper quartile 224 and maximum 235.

The middle graph, labelled *Re-sample*, shows 1000 re-sample (bootstrap) means, each as a blue vertical line approximately 0.7 cm long. The middle lines are more densely packed and the bootstrap confidence interval (203.56, 215.52) is indicated as a horizontal line in red. The re-sample means range from approximately 199 – 220.

The bottom graph is a dot plot of all the bootstrap re-sample means. There is a dot for every re-sample mean and the dots represent the vertical lines on the middle graph. The bootstrap distribution is approximately bell-shaped. The bootstrap confidence interval is drawn on the dot plot and the end points (203.56 and 215.52) are indicated by red downwards arrows. The dots below 203.56 and above 215.52 are light grey, the dots within the bootstrap confidence interval are dark grey.

Last updated September 24, 2013

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