Maths - probability

What do you plot on a cumulative frequency graph?

the upper class boundary (the bigger number)

How do you find the median on a cumulative frequency graph?

find the highest cumulative frequency and divide it by two. read across from the y-axis to convert it on the x-axis

How do you find the upper quartile of a cumulative frequency graph?

¾ × highest cumulative frequency

then convert it

How do you find the lower quartile of a cumulative frequency graph?

¼ × highest cumulative frequency

then convert it

How do you find the interquartile range?

Upper quartile - Lower quartile

What is the formula for frequency density?

frequency/class width

How do you find the mean of a frequency table?

1. Find the midpoint of each value

2. Multiply each frequency by its midpoint

3. Find the total m×f

4. Divide by the total frequency

How do you find the median of a frequency table?

1. Add up all the frequencies together

2. Find the middle position (n+1/2)

3. Work through the cumulative frequencies until you reach that number

4. Find the midpoint of the range of numbers

Probability of independent events (probability of getting A and B)

P(A and B) = P(A) × P(B)

Probability of mutually exclusive events (probability of getting A or B)

P(A or B) = P(A) + P(B)