Averages from Tables Flashcards

All 5 cards in this deck

What are the steps to find the mean from an ungrouped frequency table?

e.g. value 1 (frequency 4), value 2 (frequency 3), value 3 (frequency 3)

1. Work out $fx$ for each row: $4$, $6$, $9$
2. Find $\sum fx = 19$ and $\sum f = 10$
3. Mean $= 19 \div 10 = 1.9$

True or false? The mode of an ungrouped frequency table is the largest frequency in the table.

False. The mode is the data value that has that largest frequency.

True or false? To find the mean from a frequency table you divide $\sum fx$ by the number of rows in the table.

False. You divide by the total frequency $\sum f$.

What are the steps to find the median from an ungrouped frequency table?

e.g. value 1 (frequency 2), value 2 (frequency 3), value 3 (frequency 4)

1. Add the frequencies: $2+3+4=9$
2. Median position $=\frac{n+1}{2}=\frac{10}{2}=5$th value
3. Count through the frequencies (cumulative $2, 5, 9$): the 5th value is $2$, so the median is $2$

True or false? The median of an ungrouped frequency table is the value in the middle row of the table.

False. You must use the total frequency: find the $\frac{n+1}{2}$th value by counting through the frequencies.