which is just another way of summing all the elements, producing 480. But if you wanted to omit the

first and last elements of the array from the sum, you could write:

This expression says to add up only Gluc2 + Gluc3 + Gluc4, to get

, which would equal

330.

Π works just like ∑, except that you multiply instead of add:

SCIENTIFIC NOTATION: THE EASY WAY TO WORK WITH

REALLY BIG AND REALLY SMALL NUMBERS

Statistical analyses can generate extremely large as well as extremely small numbers, but humans are most comfortable

working with numbers that are in the range of 10s, 100s or 1,000s. Numbers much smaller than 1 (like 0.0000000000005) or

much larger than 1,000 (like 5,000,000,000,000) are difficult for humans to comprehend. So for humans, working with

extremely large or extremely small numbers is difficult and error-prone (as is working with certain humans).

Fortunately, to make it easier on all of us, we have scientific notation, which is a way to represent very small or very large

numbers to make the easier for humans to understand. Here are three different ways to express the same number in

scientific notation:

or 1.23E7, or

. All three mean “take the number 1.23, and then slide the decimal point

seven spaces to the right (adding zeros as needed).” To work this out by hand, you could start by adding extra decimal

places with zeros, like 1.2300000000. Then, slide the decimal point seven places to the right to get 12300000.000 and clean it

up to get 12,300,000.

For very small numbers, the number after the E (or e) is negative, indicating that you need to slide the decimal point to the

left. For example, 1.23e–9 is the scientific notation for 0.00000000123.

Note: Don’t be misled by the “e” that appears in scientific notation — it doesn’t stand for the 2.718 constant. You should read

it as “times ten raised to the power of.”