Question

The relationship between "strength" and "fineness" of cotton fibers was the subject of a study that produced the following data. (Give your answers correct to two decimal places.)

x, Strength	76	69	71	76	83	72	78	74	80	82
y, Fineness	4.3	4.7	4.5	4.0	4.1	4.0	5.0	4.9	4.1	4.3

(a) Draw a scatter diagram. (Do this on paper. Your instructor may ask you to turn in this work.)

(b) Find the 95% confidence interval for the mean measurement of fineness for fibers with a strength of 74.

Lower Limit
Upper Limit

(c) Find the 95% prediction interval for an individual measurement of fineness for fibers with a strength of 74.

Lower Limit
Upper Limit

Answer 1

Using excel<data<megastat<correlation/regression<regression

Here is the output:

Predicted values for: Fineness,y
		95% Confidence Interval	95% Prediction Interval
strength,x	Predicted	lower	upper	lower	upper	Leverage
74	4.4395	4.1381	4.7409	3.5261	5.3529	0.122

(a) Draw a scatter diagram.

Using excel<data<megastat<correlation/regression<scatterplot

(b) Find the 95% confidence interval for the mean measurement of fineness for fibers with a strength of 74.

Lower Limit	4.1381
Upper Limit	4.7409

(c) Find the 95% prediction interval for an individual measurement of fineness for fibers with a strength of 74.

Lower Limit	3.5261
Upper Limit	5.3529

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