# MS Excel to study Correlation between Humidity & Differential Pressure

#### Ajit Basrur

I need help with MS Excel spreadsheet to study a correlation between Humidity values and Differential Pressure in a cleanroom.

In the attached Excel spreadsheet, I am interested to see if the Humidity in ambient manufacturing area (column D) and Humidity in cleanroom (column K) had any effect on the Differential Pressures (column R).

Can some one help me with this chart?

#### Attachments

• Humidity CR7 Graph for Elsmar.xlsx
54.7 KB · Views: 202

#### Miner

##### Forum Moderator
Re: Need help with MS Excel to study correlation between Humidity & Differential Pres

Ajit,

Before looking at correlations and ultimately at regression models, it is always good to review the time based behavior of the variables.

Attached are time series plots of the three variables. It is easy to see that there is a very strong correlation between the two humidity variables. The Mfg RH usually leads the CR RH with the exception of the initial portion of the plot. On the other hand, while there appears to be a rough negative correlation between humidity and differential pressure, it was anomalous in several ways. When plotted over time on an individuals chart, it was remarkably stable. With the exception of one shift, differential pressure randomly fluctuates about a stable mean, and does follow the RH. Is it possible that the differential pressure was adjusted once (manually/automatically) in response to a major shift in RH rather than passively following the RH?

#### Attachments

• Time Series.jpg
39.4 KB · Views: 238
• I Chart of DP inWC by Stage.jpg
32.1 KB · Views: 249
• Scatterplot of CR7 RH vs Mfg RH.jpg
22.2 KB · Views: 235

#### Ajit Basrur

Re: Need help with MS Excel to study correlation between Humidity & Differential Pres

Thank you very much Miner. This is very helpful.

Yes, certain tasks were done on the air handler that could have caused the shift in RH.

Can you share the native files? Is this in Minitab?

Thanks again, Miner. Appreciate your inputs.

#### v9991

Trusted Information Resource
Re: Need help with MS Excel to study correlation between Humidity & Differential Pres

Miner...
with little more effort, we could create the other control charts as well!!...however here's one with other charts.

#### Attachments

• Humidity CR7 Graph for Elsmar.xlsx
149.2 KB · Views: 216

#### Ronen E

##### Problem Solver
Moderator
Re: Need help with MS Excel to study correlation between Humidity & Differential Pres

study a correlation between Humidity values and Differential Pressure in a cleanroom.

see if the Humidity in ambient manufacturing area (column D) and Humidity in cleanroom (column K) had any effect on the Differential Pressures (column R).

Correlation does not necessarily indicate causality. Generally and theoretically, it could be the other way around, or both could be an effect of another factor. I recommend making sure you're able to at least hypothesise a physical explanation for any assumed causality.

[Inspired by Bev D's signature ]

#### v9991

Trusted Information Resource
Re: Need help with MS Excel to study correlation between Humidity & Differential Pres

Correlation does not necessarily indicate causality. Generally and theoretically, it could be the other way around, or both could be an effect of another factor. I recommend making sure you're able to at least hypothesis a physical explanation for any assumed causality.
extending the same ...

IF you don't have hypothesis before analyzing the data; THEN don't proceed without evaluating the adequacy of data to prove the sufficiency/completeness of 'inference' / 'understanding'...

#### Miner

##### Forum Moderator
Re: Need help with MS Excel to study correlation between Humidity & Differential Pres

Can you share the native files? Is this in Minitab?

Thanks again, Miner. Appreciate your inputs.

Yes, I can. It is in Minitab 17. Are you able to open v 17 files? I can save then as v 16 or v 15 also if necessary.

#### Attachments

• Ajit.mpj
673.3 KB · Views: 165

#### Ajit Basrur

Thank you Miner. I do not have Minitab on my computer; will get assistance from the QC lab to open the file.

Replies
7
Views
4K
J
Replies
16
Views
6K
L
Replies
4
Views
2K
Luke Wilkinson
L