Chapter-2_Note

Chapter-2_Note - MATH 2300: Statistical Methods Chapter 2...

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MATH 2300: Statistical Methods Chapter 2 Section 2.1 What are the types of Data Variable A variable is any characteristic that is observed for the subjects in a study. The data values that are observed for a variable are referred to as the observations. Categorical and Quantitative variables Categorical: A variable is categorical if each observation belongs to one of a set of categories Quantitative: A variable is quantitative if observations on it take numerical values that represent different magnitudes of the variable. Ex 7: Examples for categorical variables Gender: male, female Hair color: blond, brown, red, black Blood type: A, B, AB, O Examples for quantitative variables Age Height Number of children for a family Discrete and Continuous variables A quantitative variable could be either discrete or continuous . Discrete: A quantitative variable is discrete if it’s possible values form a set of separate numbers such as 0,1,2,3,…. Continuous: A quantitative variable is continuous if its possible values form an interval Ex 8: Examples for discrete variables Number of students in a class: Only counting numbers Height of a pile of bricks of height ½” each: Only multiples of ½” Examples for continuous variables Height of a person: Can take any value in a some interval (say from 1’ to 9’) Temperature of Lubbock: Can take any value in some interval (25 to 110)
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Summarizing data using tables and graph The methods used for summarizing and ana Proportion and Percentages (relative frequ Proportion of the observations tha g G±²³´²µ¶· ¸¶¹´µº» ¹G ¹¼½²±¾¿ º¹º¿À µ´Á¼²± ¹G ¹ Percentage of the observations tha g G±²³´²µ¶· ¸¶¹´µº» ¹G ¹¼½²±¾¿ º¹º¿À µ´Á¼²± ¹G ¹ Proportions and percentages are also called Frequency Table A frequency table is a listing of possible val Ex 9: A campus press polled a sample of 300 und change in a dormitory regulation. Summary Response Frequen Support Neutral Oppose Total Categorical variables alyzing data depend on the type of the variable. uencies) at fall in a certain category ¿ºÂ¹µ½ µ ºÃ¿º ¶¿º²Ä¹±· ¹¼½²±¾¿ºÂ¹µ½ at fall in a certain category = Proportion * 100 ¿ºÂ¹µ½ µ ºÃ¿º ¶¿º²Ä¹±· ¹¼½²±¾¿ºÂ¹µ½ Å uUU d relative frequencies . lues for a variable, together with the number of obs dergraduate students in order to study students’ atti y of results of an opinion poll is as follows. ncy Proportion Percentage 150 =150/300 = 0.5 5 50 = 50/300 = 0.167 16. 100 = 100/300 = 0.333 33. 300 1 10 Variables Quantitativ variables Discrete varaibles servations for each value. titude towards a proposed
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Chapter-2_Note - MATH 2300: Statistical Methods Chapter 2...

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