Select the entire array and press the Delete key. There are usually only problems if you want to delete some, but not all of the cells in the array.
You cannot delete part of an array, so you select all of it and then delete it. You could use the Delete key to do that.
Excel has a ZTEST function. It has the format ZTEST(array, µ0, sigma).
They are the { and } symbols. They are used in conjunction with Array formulas.
After you enter your formula, press CTRL+SHIFT+ENTER at the same time. You will see the array formula displayed with brackets ({}) around it. If you type the same text, including the brackets and press just ENTER, you will not tell Excel the formula is an array and may display only text. You need to enter the formula, without the brackets, and press CTRL+SHIFT+ENTER to let Excel know it is an array. See related links for more details about array formulas.
Click on the picture and press delete.
They automatically appear as part of array formulas. You do not type them in manually. See the related question below.
When writing the function, in the table array choose the table from the relevant sheet.
An array is a list of related values of the same data type. Excel can deal with arrays and actually has some specialised array formulas. You can do things like in a single formula multiply corresponding values in two separate lists and total the result. You would type in the formula as normal: =SUM(C10:C20*D10:D20) Then press the Ctrl, shift and Enter keys, rather than just the Enter key. The formula will then appear with the braces around it to indicate that it is an array formula as follows: {=SUM(C10:C20*D10:D20)} That formula will multiply what is in C10 by D10, C11 by D11 and so on up to multiplying C20 by D20, and then total all the results in one single formula.
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It can simply be a range. It could also be an array. It will depend on the formula itself.
Use the IRR function in Excel. You need an array of values, of which at least one must be negative and one positive. You also have the option of a Guess value. It is a specialised financial function, so if you don't fully understand its use, the Excel Help facility has some assistance and there are many other sources of help too.
The reason this is happening is because you have clicked and dragged over a cell or more. To get rid of it, deselect the other cells.
You can use the LEN function to count characters in a cell. You can also use it to count characters in multiple cells. You need to know how to do array formulas to do that.