Question

Detach the data set Compliance with the command detach(Compliance).5. Open the Infants.csv data

set.

(a) Create a new variable which is the mother’s weight gain during pregnancy. Call this variable gain (gain = delweight – preweight).

(b) Sort the 68 weight gains (in a new variable sgain) and print out sgain. What is the meaning of the negative value in sgain?

(c) Obtain a scatterplot of gain against preweight. Use (plot(Infants$preweight, gain))

What does the plot suggest about the relationship between these two variables? Can you identify the mother in part (a)?

(d) Obtain a stemplot of the weight gains. How would you characterize the shape of the distribution?

(e) Obtain the mean, median of weight gain.

Are the (relative) values of the mean and median consistent with your answer to part (c)? Explain.

(f) The largest weight gain is how many standard deviations above the mean?

(g) Interpret the standard deviation in this case.

(h) There are two measures that are occasionally used in place of the mean or median as a measure of the center of the data. One is M1 = (X₇₅ + X₂₅)/2 (the mid-quartile) and the other M2 = (X₈₀ + X₂₀)/2 (the mid-quintile). Please compute these two measures for weight gain.

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