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Set3_KEY

# Set3_KEY - Homework Set#3 NAME_KEY CM MA 223 Engineering...

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Homework Set #3 NAME:______________ KEY __________________ CM:________________ MA 223, Engineering Statistics Spring 2008; 15 points possible Due date: Friday , March 28 at the BEGINNING of class (early submissions are acceptable) . You may work together on thinking through these problems, but what you turn in must be your own individual write up and work. Please show as much work as possible. It’s much easier to give partial credit when the work is all available. The data for this homework set is available in ANGEL. Please clearly label your graphs including axes … Please attach your Minitab work at the end of the homework set . You may cut and paste your Minitab work into a word or notepad document. _________________________________________________________________________________________ 1. TRUTH: The National Weather Service Forecast Office puts out its own Cricket Chip Converter: You enter the number of times a cricket chirps in 15 seconds, and the converter gives you the temperature estimated in 4 different units, including degrees Fahrenheit and Celsius. http://www.srh.noaa.gov/elp/wxcalc/cricketconvert.shtml Here is some sample data for the number of cricket chirps in 15 seconds and accompanying temperatures in degrees Fahrenheit: Make a scatterplot of this data. [Graph -> Scatterplot] Num Chirps in 15 sec 18 20 21 23 27 30 34 39 Temp (F) 57 60 64 65 68 71 74 77 (a) [+0.5] What is the predictor variable? the number of chirps in 15 seconds (b) [+0.5] What is the response variable? the temperature in (c) [+0.5] By-hand, in Maple, or in Minitab, calculate the sample sample correlation coefficient r . [ In Minitab: Stat -> Basic Statistics -> Correlation] Correlations: Num Chirps in 15 sec, Temp (F) Pearson correlation of Num Chirps in 15 sec and Temp (F) = 0.977 (d) [+0.5] The correlation coefficient r states the strength of the ____ LINEAR ______________ relationship between the predictor and response variables.

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(e) [+1] In Minitab, the commands Stat -> Regression -> Regression gave the following output. What is the least squares regression line? Write it in below in terms of and x . Round your slope and intercept to 3 decimal places. Regression Analysis: Temp (F) versus Num Chirps in 15 sec The regression equation is Temp (F) = 43.0 + 0.906 Num Chirps in 15 sec Predictor Coef SE Coef T P Constant 42.997 2.186 19.67 0.000 Num Chirps in 15 sec 0.90576 0.07983 11.35 0.000 (f) [+0.5] For each additional chirp per 15 second time interval, what is the approximate increase in Fahrenheit temperature? (g) [+0.5] What is the approximate temperature in Fahrenheit associated with 25 cricket chirps in 15 seconds? (h) [+1] The “ y - intercept” for this regression line doesn’t give us useful information about cricket chirps and temperature. Why not?
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