What are the Probabilities?

[Ed in Houston]

What is the probability of a palm surviving in your area? The probability depends on not only the average (mean) low seasonal temperature given by the zone maps but also the math term "standard diviation". The SD is measure of how far from the mean a single data point (one year's minimum) is likely to occur from the mean of a data set of yearly minimums.

It should be noted that the SD will be larger in locations more toward the center of a continent where drastic swings in temperature can occur.

In Houston it should be less, in the inland location of Orlando even less due to the peninsula effect and even less in a location like Tampa that is on the coast.

To calculate the probability of a palms survival one must first have a data set of yearly minimums and then the mean, SD and probabity of survival can be calculated.

A data set for Houston Hobby airport was located when I googled "yearly temperature minimums weather warehouse Houston hobby".

This page came up.

http://weather-warehouse.com/WeatherHistory/PastWeatherData_HoustonWilliamPHobbyArpt_Houston_TX_February.html

The page data for February came up and data for January and December can be seen by clicking on those months. The yearly minimum for each year can be determined by examining the minimums of January, February and December for each year. Hobby Airport is about 10 milies NW of my place in SE Houston.

Similarly the data for Orlando can be found by a google of "yearly minimum temperature weather warehouse Orlando international".

There is probably an easier way to get at the data. Maybe Jimbean who has probably been playing with data sets for his zone maps knows a way.

After tabulating the data of yearly minimums for Houston Hobby for the years 1990-2014, a 25 year data set, I entered the yearly minimums in the box on the web site given below and hit the calculate button. The SD and the mean was given.

http://www.rapidtables.com/calc/math/variance-calculator.htm

The SD for Houston Hobby airport yearly minimums is 3.55 and the mean is 28.36F. Once the SD and the mean is known, the probablity for any temperature occurrence can easily be calculated on the web site given below.

http://www.mathportal.org/calculators/statistics-calculator/normal-distribution-calculator.php

Many aspects of nature follow a nomal distribution as does temperature. The same applies for example people's weight distribution where one could calculate the mean and SD of a population's weight and then it could be calculated the probability of coming across someone who weighed 300 pounds.

Enter the mean and SD in the two boxes in the web site above and click the third button down beside P(X< (box) ), enter the temperature in the box that you wish to know the probablity of occurring and and click show me an explanation and compute.

Suppose I bought a plam that dies at 25 degrees or a plam that shows damage at 25 degrees and planted it near Houston Hobby airport. What is the probability that the palm will survive or be damaged?

I entered 3.55 SD and the mean 28.36 from the Houston Hobby data calculations and 25 for the probability of that temperature occurence in the box by the third button.

This example yeilded the probability of a temperature of 25 or below at or near Houston Hobby airport to be .1711 or 17%. In other words, there is a probability of 83% that the temperature will not go below 25 in any given year.

There are other factors of course. I read a research paper that showed that the Houston heat island effect was increasing the Houston night time temperature by 1.25F degrees per decade due to polpulation and building growth. And then there is climate change where the next 25 years may not look the same as the last 25 years.

If you wish to quatify the probabity of a particular temperature occuring in your area, this is the methodology.

Ed in Houston