descriptive statistics

Calculations in most spreadsheets are done by functions, also known as formulas. Every function is typed into a cell and looks like this: =Function-name( cells the function is working on ) Here are some important ones we will use in statistics. On paper, these calculations are represented by mathematical notations involving the symbol Σ, the instruction to add up a list of numbers. Make note of these as you go along. • Counting: the function shown here counts the number of numbers in cells A1 to A9: =count( A1:A9 ) This use of the same function counts the number of numbers in the entire column A: =count( A:A ) • Summation: Calculating the sum of a list of numbers in cells is carried out like this: 1 =sum( A1:A9 ) This adds, or sums, the numbers in the cells A1 to A9. To sum all numbers in the entire column A, use the function like this: =sum( A:A ) If we denote the numbers in the list by xi, for i = 1 to n, then this sum is represented mathematically as X i xi . • Sum of squares: Calculating the sum of the squares of a list of numbers in cells is carried out with this function: =sumsq( A1:A9 ) This adds, or sums, the square of the numbers in the cells A1 to A9. The specific range A1:A9 in the argument can be replaced by A:A as before. If we represent the numbers in the list as xi, then this sum of squares is represented mathematically as X i x 2 i . • Cross summation: Consider a list of paired values, in other words two lists of the same length so that each number in one list has a corresponding number in the second. For this case, the sum of the products of the corresponding values in the two lists is calculated with =sumproduct(A1:A9,B1:B9) Page 2 If xi and yi are the two lists, then this sum is denoted mathematically by X i xiyi . Note how the they both have the same index i.