This is grouped data so unless you have the raw data, you're going to have to do something to recreate variation in your data. For simplicity we can assume a flat distribution - dogs are as equally likely to be 0 as 5.

Use the `REPT()`

function to output a comma-separated list of numbers representing each group.

```
=REPT(B2&",",C2) --- where B2 is your group upper bound and C2 is the group frequency
```

At the bottom, concatenate each of those strings into one large string:

Copy this string and **Paste Special** as **Values** in a new worksheet. Use the **Text to Columns** tool on the **Data** ribbon tab to split the data into one column per value. Copy this entire range, then **Paste Special** and **Transpose** to flip this into a vertical list of values. Your data should look something like this:

Feel free to discard the horizontal row - we don't need it. Now we want to interpolate some values in column B, using a formula something like:

```
=(5*COUNTIF($A$4:A5,A5)/COUNTIF($A$4:$A$5000,A5))+(A5-5)
```

Breaking this down, we have:

```
=(5* -- your groups are increments of 5
COUNTIF($A$4:A5,A5) -- how far down a row is within a group
/
COUNTIF($A$4:$A$5000,A5) -- what the frequency is for that group
)
+(A5-5) -- add this result to the lower bound
```

Now, you can use the `QUARTILE()`

function on this list of estimated values to approximate your quartiles:

```
=QUARTILE($B$5:$B$130,1)
```