Fact, Power, Product, & Int

A mathematical function that has wide use in statistics is the factorial function.  When calculating the factorial of a number, you multiple the number by every number lower than that number all the way to the number one.  For instance, 4! is calculated as 4*3*2*1.  Factorials are fairly easy to calculate for small numbers, but much more challenging with large numbers.  The factorial function of Excel can help with this calculation process. 

Skill Builder:  Using the Factorial Function

1.	Click	Within the Cell where you want the factorial value to 
		appear.

2.	Type	The function equation.  With this function you will use 
		the following.  

		=fact(value of the factorial you wish to calculate)  

		For example, if you wanted to calculate the factorial of 8, 
		you would use the following formula:         
		=fact(8)

3.  	Press	Enter.  The value of the factorial is calculated.

Another function that you may desire to use is the power function.  This function will raise a value to a certain power.  This means that the number will be multiplied by itself as many times as the “power” specifies.  For instance, 2 raised to the 3 power is equivalent to 2*2*2.  Once again, Excel will calculate this number for you.

Skill Builder:  Using the Power Function

1.	Click	Within the Cell where you want the value, raised to a 
		power to appear.

2.	Type	The function equation.  With this function you will use 
		the following:  

		=power(the number you want to raise to a certain power, 
		the value of the power)  

		For example, if you wanted to raise the number 7 to the 
		5th power, you would use the following formula:         
		=power(7 ,5)

3.  	Press	Enter.  The value of the power is calculated.

Another function that will come into play at different times is the product function.  This is useful when you have several values and you wish to multiply these values together.

Skill Builder:  Using the Product Function

1.	Click	Within the Cell where you want the product of the 
		values to appear.

2.	Type	The function equation.  With this function you will use 
		the following:  

		=product(the addresses of the cells that you would like 
		to multiply)  

		For example, if you wanted to multiply the values of 
		cells B9 through B12, you would use the following 
		formula:         
		=product(B9:B12

3.  	Press	Enter.  The value of the product is calculated.

Another function you may find useful is the Int function.  To examine this function, open the Workers file from your data disk.

In this file we will work with the birth date to examine the age of a person.  In a data file, you would not want to simply type an age, as the age of a person is continually changing.  

When calculating a person’s age, you should use the following formula.

=today()-the cell address that contains the persons birth date.  For example =today()-A2.  When you hit enter, the number of days the person has been living is calculated.

After you have calculated the number of days, you will want to convert this number to a number of years.  To do this, use the following formula:

=(today()-A2)/365.25

When you hit enter, you will see the number of years the person has been living.  However, the number that is displayed is a decimal.  Since we don’t refer to ages in decimals, we will use the integer function to convert this number.  Use the following function:

=INT((TODAY()-A2)/365.25)

When you hit return, the person’s age will appear.  In essence, this function truncates a decimal number leaving the value as a whole integer number.  This function will continue to update as the current date changes.