Question

A researcher randomly divides 19 subjects into two groups. One group receives a new drug called RT56 for 3 months, the other a placebo (looks like RT56, but is a sugar pill). She then measures reaction time (RT) on a complex task and finds the following RT s in seconds (s): Group 1 Group 2 RT56 Placebo N=10 N=9 .456 .532 .347 .458 .435 .768 .234 .643 .521 .678 .411 .569 .398 .486 .254 .647 .391 .501 .289

Answer 1

Result:

A researcher randomly divides 19 subjects into two groups. One group receives a new drug called RT56 for 3 months, the other a placebo (looks like RT56, but is a sugar pill). She then measures reaction time (RT) on a complex task and finds the following RT s in seconds (s): Group 1 Group 2 RT56 Placebo N=10 N=9 .456 .532 .347 .458 .435 .768 .234 .643 .521 .678 .411 .569 .398 .486 .254 .647 .391 .501 .289

independent variable: treatment( RT56 and Placebo) and dependent variables: reaction time

Null Hypothesis in words and symbols.
  

Ho: There is no difference in average reaction time between RT56 and Placebo groups

H1: There is a difference in average reaction time between RT56 and Placebo groups

Ho: µ1 = µ2   H1: µ1 ≠ µ2

Compute the appropriate statistic.
  

Pooled-Variance t Test for the Difference Between Two Means
(assumes equal population variances)
Data
Hypothesized Difference	0
Level of Significance	0.05
Population 1 Sample
Sample Size	10
Sample Mean	0.3736
Sample Standard Deviation	0.0920
Population 2 Sample
Sample Size	9
Sample Mean	0.5869
Sample Standard Deviation	0.1033
Intermediate Calculations
Population 1 Sample Degrees of Freedom	9
Population 2 Sample Degrees of Freedom	8
Total Degrees of Freedom	17
Pooled Variance	0.0095
Standard Error	0.0448
Difference in Sample Means	-0.2133
t Test Statistic	-4.7611
Two-Tail Test
Lower Critical Value	-2.1098
Upper Critical Value	2.1098
p-Value	0.0002
Reject the null hypothesis

Calculated t= -4.7611

DF = n1+n2-2 =17

Table value of t with 17 DF at 0.05 level = 2.1098

Rejection Region: Reject Ho if t < -2.1098 or t > 2.1098

Calculated t = -4.7611 in the rejection region

The null hypothesis is rejected.

There is enough evidence in the data to conclude that there is a difference in average reaction time between RT56 and Placebo groups.