Question

Determine if the greatest % salinity at which bacteria was able to grow at the end of the experiment is significantly different than at the start of the experiment by using the t-test.

Pooled Data:

	Control Plates	15% salinity agar plates
1	12.67	9.23
2	12.47	9.72
3	12.78	10.25

Answer 1

Control Plates	15% salinity agar plates
12.67	9.23
12.47	9.72
12.78	10.25
12.64	9.733333333	Mean
0.157162336	0.510130702	SD
0.090737717	0.294524098	SE
3	3	N
Unpaired t test results (STUDENT T TEST)
P value and statistical significance:
The two-tailed P value equals 0.0007	(any value less than 0.05 is significant)
By conventional criteria, this difference is considered to be extremely statistically significant.
Confidence interval:
The mean of Group One minus Group Two equals 2.9067
95% confidence interval of this difference: From 2.0510 to 3.7623
Intermediate values used in calculations:
t = 9.4316
df = 4
standard error of difference = 0.308 Calculate using following formula for manual one: where X1 is mean of control, X2 is mean of saline group, S1 is standard deviation of group one, S2 SD for group 2. Result: Salinity groups are significantly different than the control one