statistics question

Can you please help me with this question. I am having trouble getting the equation. Thanks in advance!

A recent review of a compact disc distributor’s product line is summarized as follows:

Selling Price $ Number of Titles

0 to under 5 51

5 to under 10 184

10 to under 15 241

15 to under 20 1468

20 to under 25 1339

25 to under 30 255

30 to under 35 98

35 to under 40 14

Show the following are true. Be sure to demonstrate to the instructor you understand all the concepts required to arrive at the answers.
a) standard deviation is $5.449.

@MITer94

@zxcvbnm1216 you can’t compute SD exactly given only ranges of selling prices.

You can approximate by assuming that there were 51 titles selling at $2.50, 184 titles selling at $7.50, 241 titles selling at $12.50, etc. Compute the weighted average selling price xbar. Then compute the standard deviation σ given by

σ = √(∑(x - xbar)^2)/n)

where n is the number of elements (i.e. total number of titles).

Thanks @MITer94 What do the symbols mean in this equation?: σ = √(∑(x - xbar)^2)/n)
I know σ is the sign for standard deviation but i do not understand the rest of the equation

@zxcvbnm1216 If you have learned anything about standard deviation, you should have seen this formula.

∑: summation
x: index corresponding to data values (in this case, selling price of a product)
xbar: arithmetic mean of data values
^2 squared

ok thanks @MITer94