Statistics: spreadsheet vs calculator, part 1: Google Sheets compared with TI-83 Plus, normal cdf

Tutoring statistics, one encounters various electronic facilities. The tutor compares Google Sheets with the TI-83 Plus using the normal cdf.

The following is according to my understanding.

My earlier coverage of a Google Sheets way to use the normal cdf one will find in my post from January 24. Then, in my post on January 27, I show how to use the normal cdf on the TI-83 Plus. One who uses both will notice their different approaches.

The TI-83 Plus assumes the user understands the use of the normal distribution for finding the proportion of the population between two values of a normal distribution. For someone not expecting that, the lower bound requirement might come as a surprise. Yet, for someone who is used to the normal distribution, it’s very convenient. Moreover, the TI-83 Plus is not the only calculator I’ve encountered that’s set up this way.

To find, on Google Sheets, the proportion of a population between two values of a normal distribution, one can simply do two calculations, and afterward subtract. Here’s an example:

Suppose the mean mile time of track-and-field students is 345 seconds with standard deviation 34 seconds. What percent of them run the mile between 295 and 305 seconds?

Solution: To find the proportion whose run times are between 295s and 305s, the user can apply NORMDIST twice, then subtract, as follows:

Let’s imagine in Cell E5 one enters =normdist(295,345,34,1): the answer, it seems, will be 0.07070 rounded. Then, in Cell F5, one enters =normdist(305,345,34,1): the answer, it seems, will be 0.11970 rounded. Next, in Cell G5, one can enter = F5 – E5: the answer, it seems, will be 0.04900 rounded.

The meaning of the answer in Cell G5 is that the proportion of the students who run the mile between 295s and 305s is 0.049, or 4.9 percent.

To get the same answer on the TI-83 Plus, one would key in 2nd VARS 2 295,305,345,34) Enter.

Source:

support.google.com NORMDIST

Texas Instruments (1999). TI-83 Plus Graphing Calculator Guidebook. Texas Instruments Incorporated.