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STAT 200 Homework 2 Assignment




Question;1. Barium-137 m is a radioactive form of the element barium that decays very rapidly. In an experiment the radioactivity of a sample of barium-137m is measured at times 1, 3, 5 and 7. The measurement units are counts. Here are the data for one of these experiments.Time 1 3 5 7Count 578 317 203 118(a) Make two scatter plots of these data, one uses Time as x axes and the other uses Count as xaxes. Which one do you think is more appropriate? Explain why.(b) Based on the plots, describe the relationship between two variables? For example, does it appear to linear? Or are them positively related or negatively related?2. The World Bank collects data on many variables for countries throughout the world including internet use in number of users per 100 people, and birthrate in births per 1000 people. The scatter plot of 106 countries is given below.(a) Based on the plot, describe the relationship between these two variables. (b) Do you think internet use affects birthrate or is there another possible explanation for therelationship? Explain.3. * Consider the radioactive data listed in Question 1.(a) Calculate the correlation between two variables. (Show all your work)(b) Explain whether the correlation is a good summary of the relationship or not.(c) *Bonus: Also use software R to calculate the correlation in (a), for bonus. But please attach your R code and output.4. Consider the Internet use vs birthrate data in question 2. The following results are given. Mean of Internet use Mean of Birthrate Correlation 25.4 25.4 -0.73Standard Deviation of Internet use Standard Deviation of Birthrate 22.3 10.4(a) Find the numerical formula for the least squares linear regression line. (Use internet use as x axis)(b) Based on the linear regression line to predict the birthrate of a country with a 70 internet use.5. *Here are data of the measured lean body mass and metabolic rate for 12 women in a study of dieting. The researchers believe that lean body mass may influence on metabolic rate. (The data file is given by an attached link). (a) Make a scatter plot for metabolic rate depending on body mass. (b) Calculate the correlation between these two variables and write down the linear regression line.(c) Describe the nature between these two variables. (For example, strong or weak, positive or negative, ?)(d) *Bonus: If you use software R to do part (a) and (b), you can earn 1 point of bonus. But please attach your R code and output.


Paper#61828 | Written in 18-Jul-2015

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