Question

Suppose that strong claims, with weak evidence, have been made about the efficacy of an herbal treatment for attention deficit disorder (ADD). You are a research assistant for a professor who decides to empirically test the validity of these claims. You locate 10 fifthgrade students, in 10 different classrooms, who have been diagnosed with ADD. Sitting unobtrusively at the back of each classroom with stopwatch in hand, you record the number of seconds that the child with ADD is out of seat during a 20-minute period of silent reading. Each of the 10 children is then given daily doses of the herbal treatment for one month, after which you return to the classrooms to again record out-of-seat behavior during silent reading. Thus you end up with 10 pairs of observations: a pretreatment score and a posttreatment score for each student. The data collected are given below:

Pre-score 18 6 28 10 19 5 17 13 13 12

Post-score 8 5 15 7 11 0 9 4 13 3

a. Describe the independent variable and its levels.

b. Describe the dependent variable and its scale of measurement (N.O.I.R.)

c. What does the null hypothesis predict for the problem described above. (Be sure to use the variables given in the description.)

d. Conduct the appropriate statistical test of the null hypothesis using p = .05.

e. Provide an interpretation of your statistical conclusion to part D.

f. Obtain the 95% confidence interval for the sample statistic.

g. Provide an interpretation for the interval obtained in part F.

h. How does the confidence interval obtained in part F compare to your statistical conclusion in part D?

Answer 1

a) Describe the independent variable and its levels.

The independent variable is th amount of daily dose herbal treatment amd there is only one level because same amount of dose is given for 30 days for all 10 students.

b) The dependent variable is attention deficit disorder which is measured as out of seat during a 20-minute period of silent reading. scale of measurement is ratio level.

c)

H0: The ADD scores are not significantly different for pre and post treatment. ()

H1:

d)

Pre	Post	post - pre
18	8	-10
6	5	-1
28	15	-13
10	7	-3
19	11	-8
5	0	-5
17	9	-8
13	4	-9
13	13	0
12	3	-9

Descriptive Statistics

Sample	N	Mean	StDev	SE Mean
Post	10	7.50	4.67	1.48
Pre	10	14.10	6.77	2.14

Estimation for Paired Difference

Mean	StDev
= -6.60	Sd = 4.20

µ_difference: mean of (Post - Pre)

test statistic t = = -4.975

critical value = -talpha,n-1 = -1.833

alpha = 0.05 , df = n-1 =9

since t < t0.05,9 we reject null hypothesis.

e) Since the null hypothesis is rejected which means that there is strong evidence to conclude that herbal treatment significantly reduces the ADD.

f) 95% CI

t0.025,9 = 2.262

Ci = ()

95% CI for μ_difference

(-9.601, -3.599)

g) We are 95% confident that the mean difference interval lines in between  (-9.601, -3.599).

h) Since zero is not included and and it is completely negative range we conclude that herbal treatment significantly reduces the ADD.