TOSS a Coin

Toss a coin 50 times and record your results in a tally chart

h t

Yesterdays Results

1 2 3 4 5 6

37 49 46 47 48 35

Why were are results different?

Why were your results different?

• Example:Suppose we toss a coin 50 times and have 27 heads and 23 tails. We define a head as a success. The relative frequency of heads is:               n/N = 27/50 = 54%

We know the probability of a head is 50%. The difference between the relative frequency of 54% and the probability of 50% is due to small sample size.

http://argyll.epsb.ca/jreed/math7/strand4/4201.htm

Experimental Probability

• Learning Objective: To derive probabilities from experimental data

• Must use probability scale to describe the probability of events

• Should use numbers to describe the probability of an event happening

• Should use numbers to describe the probability of an event not happening

Theoretical Probability

• Previous lesson we calculated probability using equally likely outcome. A probability worked out this way is known as theoretical probability. Using words to define the outcome.

Experimental Probability

• Experimental Probability- is found by carrying out a series of experiments recording the results and using a frequency table.

• To find an experimental probability, the experiment has to be repeated several times. The rolling of dice each roll would be one TRIAL.

Experimental Probability

• Experimental Probability of an event=

Number of times the event occurs

Total number of trials

Example:A dice is thrown 50 times. The results of the 50 trials are

shown in a frequency table.

Score 1 2 3 4 5 6

Frequency 8 9 8 10 7 8

The experimental Probability of getting a 3=

3= 8 = 4

50 25The Experimental Probability of not getting a 3= 8+9+10+7+8

50

A regular dice is rolled. What is the probability of getting:a 4? …………

a) an even number? …………b) a prime number? …………

c) a number greater than 4?…………

A box contains 3 red sweets, 5 green sweets and 4 yellow sweets. A sweet is taken from the box. What is the probability of getting:

a) a green sweet? ………… b) a yellow sweet? …………

c) a red or green sweet? …………d) not a red sweet? …………

One card is taken from a pack of cards, what is the probability of picking out:a) a red card? …………

b) a club? …………c) an ace? …………

d) not an ace? …………

Class Work

• Page 262 Read Working out Probabilities and take notes

• Exercise 2- 1-12