# Stats 151 - Range, 68-95-99.7 rule, Chebychev's rule, and percentiles

Flashcards by jennabarnes12387, updated more than 1 year ago
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### Description

Chemistry 101 Stats 151 Flashcards on Stats 151 - Range, 68-95-99.7 rule, Chebychev's rule, and percentiles, created by jennabarnes12387 on 01/17/2014.

## Resource summary

 Question Answer Why is variation important in accuracy? it can demonstrate the accuracy of a measurement such as if you make a graph for the different values a weigh shows, the graph with the least variation from the correct value is the most accurate How do you calculate range? the largest value minus the smallest value How do you calculate standard deviation? take all the values collected and minus them by the middle value. place all the values in a table to see how the values deviate from the standard value When do we use standard deviation? In calculating grade for classes on the curve based on class average Describe how standard deviation is used? it is the empircal rule for the bell curve, also called the 68-95-99.7 rule or Chebychev's rule. the histogram of grades is cut into three equal part with the middle section hold 68% of the values. The middle is the average values where the values to the right are A and A+ students and the values on the left of C, D, and F students with 16% in each group How do you calculate the standard deviation from the sample mean? take a value and minus the middle value of the set of numbers from it and square the value. Then divide this number by the amount of characters minus 1. square root this value e.g. square root of (2-4)square / 4 = square root of 16/4 = 4 When calculating a students grade from a bell curve, how do you calculate each section? the middle group is equal to u. the middle right group is u+sigma. the middle left group is u-sigma. the right group is u+2sigma. the left group is u-2sigma. if applicable the far right group is u+3sigma. the far left group is u-3sigma What is the value of u in a bell curve? what is sigma? u is the dead center value or the mode. sigma is the standard deviation you want to find the grades of students on the bell curve? how do you do this? first you have to calculate sigma by a adding up all population grades and minusing the middle value from it. this number is then square and divided by the totaly number of items in the population. this value is then square rooted to find the sigma. this value will then be used in 68-95-99.7 rule when do we use Chebychev's rule? hen the graph is not a perfect bell curve What is the value of K in Chebyshev's rule? how do you calculate the percent of people in the certain range of a graph? minus the greater percent end by the smaller end. this is your k from there use the equation 1-1/K squared. this gives you a high end value and the most amount of people in this range What are percentiles? quartiles? the parts of a graph when it is divided into equal pieces? the parts of a graph when it is divided into 4 equal parts How do you find which quartile a grade falls into? you need to divide the set into 4 equal parts. find the value of each quartile by finding the median of the upper end of the sample (Q3) and minusing it from it the median of the lower half of the sample (Q1). this value is the IQR of the inter-quartile range

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