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Level III

## How to analyze the weather pattern data?

I wanted to know whether due to climate change, the precipitation in the last 16 years (2004 to 2019) had changed from the previous 15 years (1989 to 2003). Our hypothesis is that the weather patterns has changed and precipitation in the last 16 years had increased.

Here is the annual average data for different years.

 Year Precipitation (mm) 1989 384 1990 446 1991 471 1992 491 1993 507 1994 494 1995 356 1996 515 1997 438 1998 651 1999 487 2000 358 2001 353 2002 365 2003 396 2004 427 2005 551 2006 390 2007 298 2008 554 2009 451 2010 428 2011 571 2012 448 2013 818 2014 514 2015 654 2016 498 2017 429 2018 411 2019 529

I run this data using JMP after representing previous 15 years by X and last 16 years by Y. see below.

I performed permutation test. See below:

Results show that 91 per cent time I could say that the precipitation increased in the last 16 years (2004 to 2020) than previous 15 years (1989 to 2003).

My questions are as follows:

• Is the analysis correct?
• Should permutation performed with or without replacement?
• Is there any other method, which can give us better results for this kind of analysis for example “the linear trend model?”

Other questions:

When a frequency data ranges from 0 to 30 and there are so many zeros in data, should the data be transformed?  Like taking the square root of each number, taking logarithm of each number (+.5) before fitting a “regression test” or “permutation test”?

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Staff

## Re: How to analyze the weather pattern data?

Hi,

I don't know anything much about permutation analysis so I can't answer those questions.

But there are other things you could do.

...there does not appear to be a big change between these periods.

I have attached a jmp data table with your data including scripts for this plot and Fit Y by X analysis (again, no evidence for a difference between these periods).

I also used Lasso in Generalized Regression for change points analysis (JMP Pro only). This suggested a change point between 2010-2011. @clay_barker  has shown how to do this kind of thing before: https://community.jmp.com/t5/JMP-Blog/Did-LeBron-James-step-up-his-game-in-the-playoffs/ba-p/30609

I hope this helps.

Phil

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