Question 2
Install the package alr4 and load the data set allshoot.
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## [1] "Day" "n" "ybar" "SD" "Type"
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We will use the data to fit a model for the number of stem units on an apple tree based on days since dormancy. The data were collected over 106 days. However, we don't have the raw data but only the daily summary: On a specific day ( Day , the number of days from dormancy), we have the average value of number of stem units ( ybar ) obtained from the sample shoots and the sample standard deviation (SD). In the data set, n represents the number of shoots sampled for a given day. Our goal is to fit a model for ybar using Days. There is another variable Type in the data set, with for long shoots and 0 for short shoots.
Plot the scatter plot matrix for data.
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2. Plot scatter plot ybar vs Days for the two types in the same plot but using different colors or symbols for the two types.
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3. Fit a regression on ybar on Days, Type and their interaction. Summarize the fitted model. Check the residuals and perform diagnostics. Comment on any issues you see if any.
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4. Give 95% confidence intervals of the coefficients.
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5. Note that ybar is an average. We know that var(ar{x} )=(sigma ^(2))/(n). This suggests that we use a weighted least squares with weight based on n. Do this weighted regression. Give 95% confidence intervals of the coefficients. Compare them to those from part (4).
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6. Plot the data and fitted values vs Day for the two types in the same plot but different colors or symbols.
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Question 2
Install the package alr4 and load the data set allshoot
Show
Xa[I] "n"
"ybar" "SD"
"Type"
Show
We will use the data to fit a model for the number of stem units on an apple tree based on days since dormancy. The data were collected over 106 days.However,we don't have the raw data but only the daily summary:On a specific day(Day,the number of days from dormancy),we have the average value of number of stem units (ybar) obtained from the sample shoots and the sample standard deviation ( sd. In the data set, n represents the number of shoots sampled for a given day. Our goal is to fit a model for ybar using Days .There is another variable Type in the data set, with 1 for long shoots and o for short shoots
1.Plot the scatter plot matrix for data.
Answer:
2.Plot scatter plot ybar vs Days for the two types in the same plot but using different colors or symbols for the two types
Answer:
3.Fit a regression on ybar on Days, Type and their interaction.Summarize the fitted model.Check the residuals and perform diagnostics Comment on any issues you see if any
Answer:
4.Give 95% confidence intervals of the coefficients
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5. Note that ybar is an average.We know that var(X)= 2/m. This suggests that we use a weighted least squares with weight based on n . Do this weighted regression. Give 95% confidence intervals of the coefficients.Compare them to those from part (4)
Answer
6.Plot the data and fitted values vs Day for the two types in the same plot but different colors or symbols
Answer:
