1. An experiment investigated the effect of vegal nerve stimulation on in- sulin
ID: 3074522 • Letter: 1
Question
1. An experiment investigated the effect of vegal nerve stimulation on in- sulin secretion. The subjects were mongrel dogs with varying body weights. The table 1 gives the amount of immunoreactive insulin in pancreatic venous plasma just before stimulation of the left vagus nerve (X) and amount measured 5 min after stimulation (Y) for seven dogs. Dog 1 2 3456 X 350 200 240 290 90 370 240 Y 480 130 250 310 280 1450 280 Table 1: Blood levels if immunoreaction insulin (a) Carry out a paired t-test to test the hypotheses of no effect against the alternative that stimulation of the vagus nerve increases the blood level of immunoreactive insulin. (b) Carry out a Sign rank test and compare the result to part (a) 2. A study was conducted to investigate a social skills training program for alcoholics. Twenty four "alcohol-dependent" male inpatients (one missing) at an alcohol treatment center were randomly assigned to two groups. The control patients were given a traditional treatment program. The treatment group patients were given the traditional treatment pro- gram plus a class in social skills training (SST). The table below provide the alcohol intake for 1 year. Control 1042 1617 1180 973 1552 1251 1151 1511 728 1079 951 1319 SST 874 389 612 798 1152 893 541 741 1064 862 213 Table 2: Alcohol intake for 1 year (a) Test for differences between the two groups using a permutation test at 5% significance level. (b) Test for differences using the Wilcoxon rank-sum test at 5% signifi- cance level. (e) Compare the results you obtained in part (a) and (b)Explanation / Answer
X Y
350 480
200 130
240 250
290 310
90 280
370 1450
240 280
a)
Paired T for X - Y
N Mean StDev SE Mean
X 7 254 95 36
Y 7 454 451 170
Difference 7 -200 397 150
95% upper bound for mean difference: 92
T-Test of mean difference = 0 (vs < 0): T-Value = -1.33 P-Value = 0.116
since p-value > 0.05
there is not sufficient evidence that mean increases
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