Statistics

OP

Original post by mqb2766

Sure, there are a few similar ways if doing it.

For the future, can you include your current attempt when asking questions? Its easier to work out what help you need.

Oh ok. I will.

Reply 22

OP

A shopkeeper takes 12 bags of coins to the bank. The bags contain the following numbers of coins:
150, 163, 158, 165, 172, 152, 160, 170, 156, 162, 159, 175
Each bag contains coins of the same value, and the shopkeeper has at least one bag containing coins with dollar values of 0.10, 0.25, 0.50 and 1.00 only.
What is the greatest possible value of all the coins in the 12 bag?

Now I'm confused about what they're asking in the question. Can someone give me some hints on how to solve it? The answer is $1615

Reply 23

There must be at least
* one bag of 10 cents
* one bag of 25 cents
* one bag of 50 cents
* one bag of dollars
How do you make this as large as possible.

Reply 24

OP

Brilliant! Just what I needed. Thanks a lot.

Reply 25

OP

The frequency densities of the four classes in a histogram are in the ratio 4:3:2:1. The frequencies of these classes are in the ratio 10:15:24:8.
Find the total width of the histogram given that the narrowest class interval is represented by a column of width 3cm.

How to do this?

Reply 26

ghostwalker

17

Original post by Heidi002

The frequency densities of the four classes in a histogram are in the ratio 4:3:2:1. The frequencies of these classes are in the ratio 10:15:24:8.
Find the total width of the histogram given that the narrowest class interval is represented by a column of width 3cm.

How to do this?

Couple of thoughts to get you started.

If items are in a certain ratio, what can you deduce about their actual values - how do the two relate? So, how can you express the actual values in terms of the ratios? You will need to introduce a variable.

What's the relationship between class width, frequency density, and frequency?

(edited 4 years ago)

Reply 27

OP

Original post by ghostwalker

Couple of thoughts to get you started.

If items are in a certain ratio, what can you deduce about their actual values - how do the two relate? So, how can you express the actual values in terms of the ratios? You will need to introduce a variable.

What's the relationship between class width, frequency density, and frequency?

Frequency density= Frequency/Class width.
But do I require only one variable or two? As there are two ratios.

Reply 28

Original post by Heidi002

The frequency densities of the four classes in a histogram are in the ratio 4:3:2:1. The frequencies of these classes are in the ratio 10:15:24:8.
Find the total width of the histogram given that the narrowest class interval is represented by a column of width 3cm.

How to do this?

Can you sketch the bars? The frequencies represent area and the densities the height. Put unknown(s) in if necessary instead of having ratios. You should be able to work out which is the narrowest one (3cm) hence work out the total area.

Reply 29

ghostwalker

17

Original post by Heidi002

Frequency density= Frequency/Class width.
But do I require only one variable or two? As there are two ratios.

One for each set of ratios, since there's no requirement for the multiplying factor to be the same in each of the two sets.

Reply 30

OP

Ok thanks for your help. If I face further problems I'll let you know. Logging off now.

Reply 31

OP

Hello. I am facing problem in solving this question:
In a simple model of the weather in October, each day is classified as either fine or rainy. The probability that a fine day is followed by a fine day is 0.8. The probability that a rainy day is followed by a fine day is 0.4. The probability that 1 October is fine is 0.75.
a) Find the probability that 2 October is fine and the probability that 3 October is fine.

My approach:
Given, P(F and F) = 0.8
➡️P(F) × P(F|F) = 0.8
➡️0.75 × P(F|F) = 0.8
Now P(F|F) comes 1.067😳

Reply 32

Original post by Heidi002

Hello. I am facing problem in solving this question:
In a simple model of the weather in October, each day is classified as either fine or rainy. The probability that a fine day is followed by a fine day is 0.8. The probability that a rainy day is followed by a fine day is 0.4. The probability that 1 October is fine is 0.75.
a) Find the probability that 2 October is fine and the probability that 3 October is fine.

My approach:
Given, P(F and F) = 0.8
➡️P(F) × P(F|F) = 0.8
➡️0.75 × P(F|F) = 0.8
Now P(F|F) comes 1.067😳

The conditionals are 0.8 and 0.4, so
p(F|F) = 0.8
p(F|R) = 0.4
Where the first argument is next days weather and the second is today's weather.
Can you take this forward?

(edited 4 years ago)

Reply 33

OP

Original post by mqb2766

The conditionals are 0.8 and 0.4, so
p(F|F) = 0.8
p(F|R) = 0.4
Where the first argument is next days weather and the second is today's weather.
Can you take this forward?

So 0.8 × 0.75 = 0.6 but the answer is 0.7

Reply 34

Original post by Heidi002

So 0.8 × 0.75 = 0.6 but the answer is 0.7

Could it not rain on the first?
You could draw a simple tree to represent the problem.

Reply 35

OP

Original post by mqb2766

Could it not rain on the first?
You could draw a simple tree to represent the problem.

Rain on the first. Yes! That's it! I got it. Thanks.

Reply 36

OP

Ok. So here's a new problem:
A golfer hits a grade B ball into the pond. Including the golfer's ball there are then six grade C, ten grade B and four grade A balla in the pond. The golfer uses a fishing net and catches four balls. The event Z is defined as:
Z: The catch includes the golfer's own ball
Assuming the catch is a random selection from the balls, determine P(Z).
What to start with?

Reply 37

Original post by Heidi002

Ok. So here's a new problem:
A golfer hits a grade B ball into the pond. Including the golfer's ball there are then six grade C, ten grade B and four grade A balla in the pond. The golfer uses a fishing net and catches four balls. The event Z is defined as:
Z: The catch includes the golfer's own ball
Assuming the catch is a random selection from the balls, determine P(Z).
What to start with?

If the net caught 2 balls how might you work it out?I
What combinations could occur?

(edited 4 years ago)

Reply 38

OP

Original post by mqb2766

If the net caught 2 balls how might you work it out?I
What combinations could occur?

The question says four balls are caught in the net. But as you are asking, the combinations can be: both grade B ball, one grade B ball and one grade A ball, one grade B ball and one grade C ball.

Reply 39