In Statistics we play with data. data is in organized form rather than raw data.

Grouped vs. Ungrouped Data

Grouped data : Organized data is presented in a tabular form

Ungrouped Data: Unorganized data presented as raw data.

interval:

Next interval must be start where previous left. if that is not a case during problem solving we have to make new interval.

Lets understand the concept 

1. Mean for Grouped Data: 

Mean = ∑fi xi / ∑fi

Here,
∑  sigma represents the summation
xi  represents midpoint 
fi  represents the number of observations .

2.Median for Grouped Data: 

Median

3. Mode for Grouped Data: 

Mode