In: Statistics and Probability
A pediatric nurse is studying the number of hours infants sleep daily. He reviewed data from eight randomly selected patients from the pediatric ward of the local hospital. The results were as follows, where x is the infant’s age in months, and y is the number of hours the infant slept daily: \
X 2 1 7 6 14 15 10 9
Y 14.50 15.00 14.25 13.5 12.75 12.00 13.25 13.75
(a) Construct the scatter plot that represents this data. [COMMENTS & HINTS: Include a descriptive title; label the axes.]
(b) Determine the centroid for this data set.
(c) Determine the line of best fit or trend line that models this data. [COMMENTS & HINTS: Construct the scatter plot in order to identify the trend line from it. Round off to the nearest thousandths is necessary.]
(d) Determine the correlation coefficient, r, which characterizes the association between these two variables.
(e) Describe verbally the association between the two variables.
(f) Compute the coefficient of determination, 2 r .
(g) What percentage of the variability between the two variables is not due to the relationship between them?
(h) Approximately how many hours would this linear regression model predict that a twelvemonth old baby would sleep daily?
(a)
(b)
mean= | 8 | 13.625 |
population sd= | 4.743 | 0.910 |
median= | 8 | 13.625 |
(c) y = - 15.06-0.180x
following regression analysis information has been generated using ms-excel
SUMMARY OUTPUT | ||||||||
Regression Statistics | ||||||||
Multiple R | 0.94114 | |||||||
R Square | 0.885744 | |||||||
Adjusted R Square | 0.866702 | |||||||
Standard Error | 0.355186 | |||||||
Observations | 8 | |||||||
ANOVA | ||||||||
df | SS | MS | F | Significance F | ||||
Regression | 1 | 5.868056 | 5.868056 | 46.51376 | 0.000488 | |||
Residual | 6 | 0.756944 | 0.126157 | |||||
Total | 7 | 6.625 | ||||||
Coefficients | Standard Error | t Stat | P-value | Lower 95% | Upper 95% | Lower 95.0% | Upper 95.0% | |
Intercept | 15.06944 | 0.246223 | 61.20249 | 1.28E-09 | 14.46696 | 15.67193 | 14.46696 | 15.67193 |
X Variable 1 | -0.18056 | 0.026474 | -6.8201 | 0.000488 | -0.24534 | -0.11578 | -0.24534 | -0.11578 |
(d) correlation coefficeint=0.9411
(e) positive and strong association
(f) coefficient of determination=0.8857=88.57%
(g) percentage of the variability between the two variables is not due to the relationship between them?
100-88.57=11.43%
(h) for x=12, y= - 15.06-0.180*12=12.9
answer is 12.9 hours