Question

Objective: Analyze a subset of data from a published research paper using Excel. This will focus on data manipulation in Excel, including plot generation, if-statements, and conditional formatting. You are given the relative abundances (fraction of the total number of microorganisms observed) of different types of microorganisms. One set was exposed to PFAAs, another set was not. Each set consists of three different replicates, or repeat trials.

Problem: Check the statistical significance of each test, i.e., test whether there is a significant difference in relative abundance of each microorganism when it was exposed to PFAAs. We will use the Student’s T-Test, however, we must determine which type of T-Test to use. We will consider a final p-value of less than 0.05 to be significant by following the steps.

Microorganism   PFAA-1   PFAA-2   PFAA-3   No-1   No-2   No-3
Methanobacterium   0.002686341   0.003385728   0.005059022   0.000033   0   0
Bacteroidales   0.001686341   0.003372681   0.003372681   0.008431703   0.010118044   0.015177066
Porphyromonadaceae   0.160202361   0.118043845   0.10623946   0.030354132   0.042158516   0.048903879
WCHB1-05   0   0.000025   0   0.001686341   0   0.001686341
Dehalococcoides   0.003372681   0.005059022   0.005059022   0.053962901   0.062394604   0.065767285
Clostridiales   0   0.001686341   0.003372681   0.008431703   0.005059022   0
Sedimentibacter   0.092748735   0.045531197   0.05227656   0.059021922   0.059021922   0.065767285
Christensenellaceae   0   0.001686341   0.003372681   0.008431703   0.005059022   0
Coprococcus   0.003372681   0.003372681   0.001686341   0   0   0.001686341
Ruminococcaceae   0   0.006745363   0.003372681   0.003372681   0.005059022   0.005059022
Oscillospira   0   0.001686341   0   0   0.001686341   0.005059022
Veillonellaceae   0.259696459   0.279932546   0.328836425   0.222596965   0.225969646   0.249578415
Desulfovibrionaceae   0.057335582   0.038785835   0.02698145   0.02529511   0.028667791   0.028667791
Desulfovibrio   0.006745363   0.001686341   0.006745363   0.005059022   0.001686341   0.013490725
Treponema   0.064080944   0.060708263   0.067453626   0.175379427   0.121416526   0.133220911
                      

Answer 1

In this case we are going to use a 2 independent samples test, because we are comparing the means from 2 different samples (Unpaired t test).

- Methanobacterium

P value and statistical significance:
  The two-tailed P value equals 0.0130
  By conventional criteria, this difference is considered to be statistically significant.

Confidence interval:
  The mean of Group One minus Group Two equals 0.00303603450
  95% confidence interval of this difference: From 0.00153142548 to 0.00454064352

The P value is lower than 0.05, it means the relative abundance is significantly different between treatments

- Bacteroidales

P value and statistical significance:
  The two-tailed P value equals 0.0160
  By conventional criteria, this difference is considered to be statistically significant.

Confidence interval:
  The mean of Group One minus Group Two equals -0.00843170333
  95% confidence interval of this difference: From -0.01427122533 to -0.00259218134

The P value is lower than 0.05, it means the relative abundance is significantly different between treatments

- Porphyromonadaceae

P value and statistical significance:
  The two-tailed P value equals 0.0071
  By conventional criteria, this difference is considered to be very statistically significant.

Confidence interval:
  The mean of Group One minus Group Two equals 0.08768971300
  95% confidence interval of this difference: From 0.03978935881 to 0.13559006719

The P value is higher than 0.05, it means the relative abundance is not significantly different between treatments

- WCHB1-05

P value and statistical significance:
  The two-tailed P value equals 0.4226
  By conventional criteria, this difference is considered to be not statistically significant.

Confidence interval:
  The mean of Group One minus Group Two equals -0.00084317050
  95% confidence interval of this difference: From -0.00447103874 to 0.00278469774

The P value is higher than 0.05, it means the relative abundance is not significantly different between treatments

- Dehalococcoides

P value and statistical significance:
  The two-tailed P value is less than 0.0001
  By conventional criteria, this difference is considered to be extremely statistically significant.

Confidence interval:
  The mean of Group One minus Group Two equals -0.05621135500
  95% confidence interval of this difference: From -0.06608194819 to -0.04634076181

The P value is lower than 0.05, it means the relative abundance is significantly different between treatments

- Clostridiales

P value and statistical significance:
  The two-tailed P value equals 0.7345
  By conventional criteria, this difference is considered to be not statistically significant.

Confidence interval:
  The mean of Group One minus Group Two equals -0.00084317033
  95% confidence interval of this difference: From -0.00805443758 to 0.00636809692

The P value is higher than 0.05, it means the relative abundance is not significantly different between treatments

- Sedimentibacter

P value and statistical significance:
  The two-tailed P value equals 0.8875
  By conventional criteria, this difference is considered to be not statistically significant.

Confidence interval:
  The mean of Group One minus Group Two equals 0.00224845433
  95% confidence interval of this difference: From -0.03916100882 to 0.04365791749

The P value is higher than 0.05, it means the relative abundance is not significantly different between treatments

- Christensenellaceae

P value and statistical significance:
  The two-tailed P value equals 0.5091
  By conventional criteria, this difference is considered to be not statistically significant.

Confidence interval:
  The mean of Group One minus Group Two equals -0.00252951083
  95% confidence interval of this difference: From -0.01330008625 to 0.00824106459

The P value is higher than 0.05, it means the relative abundance is not significantly different between treatments

- Coprococcus

P value and statistical significance:
  The two-tailed P value equals 0.0305
  By conventional criteria, this difference is considered to be statistically significant.

Confidence interval:
  The mean of Group One minus Group Two equals 0.00281056733
  95% confidence interval of this difference: From 0.00050111298 to 0.00512002168

The P value is lower than 0.05, it means the relative abundance is significantly different between treatments

- Ruminococcaceae

P value and statistical significance:
  The two-tailed P value equals 0.6087
  By conventional criteria, this difference is considered to be not statistically significant.

Confidence interval:
  The mean of Group One minus Group Two equals -0.00112422700
  95% confidence interval of this difference: From -0.00675133150 to 0.00450287750

The P value is higher than 0.05, it means the relative abundance is not significantly different between treatments

- Oscillospira

P value and statistical significance:
  The two-tailed P value equals 0.3486
  By conventional criteria, this difference is considered to be not statistically significant.

Confidence interval:
  The mean of Group One minus Group Two equals -0.00168634067
  95% confidence interval of this difference: From -0.00610060440 to 0.00272792306

The P value is higher than 0.05, it means the relative abundance is not significantly different between treatments

- Veillonellaceae

P value and statistical significance:
  The two-tailed P value equals 0.0629
  By conventional criteria, this difference is considered to be not quite statistically significant.

Confidence interval:
  The mean of Group One minus Group Two equals 0.05677346800
  95% confidence interval of this difference: From -0.00488812235 to 0.11843505835

The P value is higher than 0.05, it means the relative abundance is not significantly different between treatments

- Desulfovibrionaceae

P value and statistical significance:
  The two-tailed P value equals 0.2044
  By conventional criteria, this difference is considered to be not statistically significant.

Confidence interval:
  The mean of Group One minus Group Two equals 0.01349072500
  95% confidence interval of this difference: From -0.01123506276 to 0.03821651276

The P value is higher than 0.05, it means the relative abundance is not significantly different between treatments

- Desulfovibrio

P value and statistical significance:
  The two-tailed P value equals 0.6873
  By conventional criteria, this difference is considered to be not statistically significant.

Confidence interval:
  The mean of Group One minus Group Two equals -0.00168634033
  95% confidence interval of this difference: From -0.01249903346 to 0.00912635280

The P value is higher than 0.05, it means the relative abundance is not significantly different between treatments

- Treponema

P value and statistical significance:
  The two-tailed P value equals 0.0086
  By conventional criteria, this difference is considered to be very statistically significant.

Confidence interval:
  The mean of Group One minus Group Two equals -0.07925801033
  95% confidence interval of this difference: From -0.12505267150 to -0.03346334917

The P value is lower than 0.05, it means the relative abundance is significantly different between treatments