In: Statistics and Probability
1. Doctors obtained the data below on the number of recovery days in the hospital using the new and old gastric bypass surgery procedures. Using the new and old surgery procedures, do the data provide sufficient evidence to conclude that the mean number of recovery days in the hospital is smaller with the new surgery procedure than with the old procedure? Use the appropriate statistical test to determine if using new surgery procedure results in a smaller mean number of recovery days. All appropriate statistical procedures/tests should be done with 5% P-value or 95% Confidence Interval.
New gastric bypass surgery procedure | 7 | 9 | 5 | 10 | 8 | 7 | 8 | 7 | 6 | 7 | 7 | 7 | 7 | 8 | ||
Old gastric bypass surgery procedure | 6 | 7 | 18 | 14 | 9 | 9 |
Click here for the Bypass_surgery-PA#23 data. (3 points)
Difference Scores Calculations
Treatment 1
N1: 14
df1 = N - 1 = 14 - 1 = 13
M1: 7.36
SS1: 19.21
s21 =
SS1/(N - 1) = 19.21/(14-1) =
1.48
Treatment 2
N2: 6
df2 = N - 1 = 6 - 1 = 5
M2: 10.5
SS2: 105.5
s22 =
SS2/(N - 1) = 105.5/(6-1) = 21.1
T-value Calculation
s2p =
((df1/(df1 +
df2)) * s21) +
((df2/(df2 +
df2)) * s22) =
((13/18) * 1.48) + ((5/18) * 21.1) = 6.93
s2M1 =
s2p/N1
= 6.93/14 = 0.49
s2M2 =
s2p/N2
= 6.93/6 = 1.15
t = (M1 -
M2)/√(s2M1
+ s2M2) =
-3.14/√1.65 = -2.45
The t-value is -2.44696. The p-value is .01245.