Chapter 1: Why is my evil lecturer forcing me to learn statistics?

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Gregory Mitchell
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1 Chapter : Why is my evil lecturer forcing me to learn statistics? Labcoat Leni s Real Research Is Friday the 3th Unlucky? Problem Scanlon, T. J., et al. (3). British Medical Journal, 3, 8 8. Many of us are superstitious, and a common superstition is that Friday the 3th is unlucky. Most of us don t literally think that someone in a hockey mask is going to kill us, but many people are wary. Scanlon and colleagues, in a tongue-in-cheek study (Scanlon, Luben, Scanlon, & Singleton, 3), looked at accident statistics at hospitals in the South West Thames region of the UK. They took statistics both for Friday the 3th and Friday the th (the week before) in different months in 8,, and 2. They looked at both emergency admissions of accidents and poisoning, and also transport accidents. Date October 8 July September December March 2 November 2 Accidents and Poisoning Friday th Friday 3th Traffic Accidents Friday th Friday 3th Calculate the mean, median, standard deviation and interquartile range for each type of accident and on each date. Solution Let s begin with accidents and poisoning on Friday the th. First, arrange the scores in ascending order:,,,,,. The median: The median will be the (n + )/2th score. There are scores, so this will be the /2 3.th. The 3.th score in our ordered list is half way between the 3rd and th scores which is (+)/2 accidents. The mean: The mean is accidents:

2 will be the (3+)/2 2nd score below the mean. Therefore, the lower quartile is accident. highest 3 scores, the median will be the (3+)/2 2nd score above the mean. Therefore, the upper quartile is accidents. The interquartile range: This is the difference between the upper and lower quartiles: 8 accidents. To calculate the sum of squares, first take the mean from each score, then square this difference, and finally, add So, the sum of squared errors is: The variance is the sum of squared errors divided by the degrees of freedom (N - ): sum of squares 3.2 variance Next let s look at accidents and poisoning on Friday the 3th. First, arrange the scores in ascending order:,,,,,. The median: The median will be the (n + )/2th score. There are scores, so this will be the /2 3.th. The 3.th score in our ordered list is half way between the 3rd and th scores which is (+)/2 accidents. The mean: The mean is accidents: will be the (3+)/2 2nd score below the mean. Therefore, the lower quartile is accidents.

3 highest 3 scores, the median will be the (3+)/2 2nd score above the mean. Therefore, the upper quartile is accidents. The interquartile range: This is the difference between the upper and lower quartiles: 2 accidents. So, the sum of squared errors is: The variance is the sum of squared errors divided by the degrees of freedom (N - ): sum of squares.8 variance.8.8 Next, let s look at traffic accidents on Friday the th. First, arrange the scores in ascending order: 3,,,,,. The median: The median will be the (n + )/2th score. There are scores, so this will be the /2 3.th. The 3.th score in our ordered list is half way between the 3rd and th scores. The 3rd score is and the th score is. Therefore the 3.th score is (+)/2. accidents. The mean: The mean is. accidents: will be the (3+)/2 2nd score below the mean. Therefore, the lower quartile is accidents.

4 highest 3 scores, the median will be the (3+)/2 2nd score above the mean. Therefore, the upper quartile is accidents. The interquartile range: This is the difference between the upper and lower quartiles: accidents So, the sum of squared errors is: The variance is the sum of squared errors divided by the degrees of freedom (N - ): sum of squares.. variance Finally, let s look at traffic accidents on Friday the 3th. First, arrange the scores in ascending order:,, 2, 2, 3,. The median: The median will be the (n + )/2th score. There are scores, so this will be the /2 3.th. The 3.th score in our ordered list is half way between the 3rd and th scores. The 3rd score is 2 and the th score is 2. Therefore the 3.th score is (2+2)/2 2 accidents. The mean: The mean is.83 accidents: will be the (3+)/2 2nd score below the mean. Therefore, the lower quartile is accidents.

5 highest 3 scores, the median will be the (3+)/2 2nd score above the mean. Therefore, the upper quartile is 3 accidents. The interquartile range: This is the difference between the upper and lower quartile: 3 3 accidents So, the sum of squared errors is: The variance is the sum of squared errors divided by the degrees of freedom (N - ): sum of squares.8 2. s variance 2. 3.

Chapter 1: Why is my evil lecturer forcing me to learn statistics?

Chapter 1: Why is my evil lecturer forcing me to learn statistics? Labcoat Leni s Real Research Is Friday the 13th Unlucky? Problem Scanlon, T. J., et al. (1993). British Medical Journal, 307, 1584 158.