Statistics-1
1.One thousand candidates sit an examination. The distribution of marks is shown in the following grouped frequency table. Marks|1–10|11–20|21–30|31–40|41–50|51–60|61–70|71–80|81–90|91–100| Number of candidates|15|50|100|170|260|220|90|45|30|20|

(a)Copy and complete the following table, which presents the above data as a cumulative frequency distribution. (3)
Mark|£10|£20|£30|£40|£50|£60|£70|£80|£90|£100|
Number of candidates|15|65|||||905||||
(b)Draw a cumulative frequency graph of the distribution, using a scale of 1 cm for 100 candidates on the vertical axis and 1 cm for 10 marks on the horizontal axis. (5)
(c)Use your graph to answer parts (i)–(iii) below,
(i)Find an estimate for the median score.
(2)
(ii)Candidates who scored less than 35 were required to retake the examination. How many candidates had to retake?
(3)
(iii)The highest-scoring 15% of candidates were awarded a distinction. Find the mark above which a distinction was awarded.
(3)
(Total 16 marks)
2.At a conference of 100 mathematicians there are 72 men and 28 women. The men have a mean height of 1.79 m and the women have a mean height of 1.62 m. Find the mean height of the 100 mathematicians. (Total 4 marks)

3.The mean of the population x1, x2, ........ , x25 is m. Given that = 300 and = 625, find
(a)the value of m;
(b)the standard deviation of the population.
(Total 4 marks)
4.A supermarket records the amount of money d spent by customers in their store during a busy period. The results are as follows: Money in $ (d)|0–20|20–40|40–60|60–80|80–100|100–120|120–140| Number of customers (n)|24|16|22|40|18|10|4|

(a)Find an estimate for the mean amount of money spent by the customers, giving your answer to the nearest dollar ($). (2)
(b)Copy and complete the following cumulative frequency table and use it to draw a cumulative frequency graph. Use a scale of 2 cm to represent $20 on the horizontal axis, and 2 cm to represent 20 customers on...

...TUI
Frequency Distributions
Module 3/Case
10/148/2012
Professor Kuleshov
Frequency Distributions
This assignment is based on Frequency Distributions and will include the following information:
1. The ability to describe the information provided by the StandardDeviation.
2. The ability to use the StandardDeviation to calculate the percentage of occurrence of a variable either above or below a particular value.
3. The ability to describe a normal distribution as evidenced by a bell shaped curve as well as the ability to prepare a distribution chart from a set of data (module 3 Case).
Part 1
(1) To get the best deal on a CD player, Tom called eight appliance stores and asked the cost of a specific model. The prices he was quoted are listed below:
$ 298 $ 125 $ 511 $ 157 $ 231 $ 230 $ 304 $ 372 Find the Standarddeviation
$ 298 + $ 125+ $ 511+ $ 157+ $ 231+ $ 230+ $ 304+ $ 372= 2228/8 = 278.5(subtract from #s)
19,-153, 232, -121, -47, -48, 25, 93 (square numbers)
380, 2356, 54056, 14762, 2256, 2352, 650, 8742 = 106(added)
(Divide by 7) 15251 (take square root) StandardDeviation = approximately 123.
(2) When investigating times required for drive-through service, the following results (in seconds) were...

...Deviation
Definition:
Behavior commonly seen in children that is the result of some obstacle to normal development such behavior may be commonly understand as negative (a timid child, a destructive child) or positive (a quite child), both positive and negative deviation will disappear once the child begins to concentrate on a piece of work freely chosen by him.
The physical deforms are easier to identify. This can be by birth due to an accident etc… and most such physical deforms can be either cured. However, deforms that take place in development of psychological aspects of a child are not only threat to building the character and the personality of the child also you find certain physical deforms in curable in medicine.
Dr. Montessori, according to her she fugues deviated children are.
The naughty children act and react very strong as a result of severe treatment they have received. So their behavior is cruel from others.
The weak children are always mistaken for good children and parent are happy because of their timidly and but they are lazy and afraid of everything.
The bright children are very imaginative and live in their own fantasy world.
Deviations shown by the strong and weak children are:
In the absorbent mind Montessori discussed deviation shown by the strong, meaning those who resist and overcome the obstacles they meet and deviation...

...I'll be honest. Standarddeviation is a more difficult concept than the others we've covered. And unless you are writing for a specialized, professional audience, you'll probably never use the words "standarddeviation" in a story. But that doesn't mean you should ignore this concept.
The standarddeviation is kind of the "mean of the mean," and often can help you find the story behind the data. To understand this concept, it can help to learn about what statisticians call normal distribution of data.
A normal distribution of data means that most of the examples in a set of data are close to the "average," while relatively few examples tend to one extreme or the other.
Let's say you are writing a story about nutrition. You need to look at people's typical daily calorie consumption. Like most data, the numbers for people's typical consumption probably will turn out to be normally distributed. That is, for most people, their consumption will be close to the mean, while fewer people eat a lot more or a lot less than the mean.
When you think about it, that's just common sense. Not that many people are getting by on a single serving of kelp and rice. Or on eight meals of steak and milkshakes. Most people lie somewhere in between.
If you looked at normally distributed data on a graph, it would look something like this:
The x-axis (the horizontal one) is the value in question......

...StandardDeviation (continued)
L.O.: To find the mean and standarddeviation from a frequency table.
The formula for the standarddeviation of a set of data is [pic]
Recap question
A sample of 60 matchboxes gave the following results for the variable x (the number of matches in a box):
[pic].
Calculate the mean and standarddeviation for x.
Introductory example for finding the mean and standarddeviation for a table:
The table shows the number of children living in a sample of households:
|Number of children, x |Frequency, f |xf |x2f |
|0 |14 |0 × 14 = 0 |02 × 14 = 0 |
|1 |12 |1 × 12 = 12 | |
|2 |8 | | |
|3 |6 | |32 × 6 = 54 |
|TOTAL...

...StandardDeviation
objective
• Describe standarddeviation and
it’s importance in biostatistics.
Measure of Dispersion
• Indicates how widely the scores
are dispersed around the central
point (or mean.)
-StandarddeviationStandardDeviation.
• The most commonly used method
of dispersion in oral hygiene.
• The larger the standarddeviation,
the wider the distribution curve.
StandardDeviation
• SD, , (sigma)
• Indicates how subjects differ from
the average of the group/ the more
they spread out, the larger the
deviation
• Based upon ALL scores, not just
high/low or middle half
• Analyzes descriptively the spread of
scores around the mean
– 14+ 2.51 = Mean of 14 and SD of
2.51
StandardDeviation
• The spread of scores around the
mean:
• For example, if the mean is 60 and
the standarddeviation 10, the
lowest score might be around 30,
and the highest score might be
around 90.
StandardDeviation &
Variance
Usefulness
• When comparing the amount of dispersion in
two data sets.
• Greater variance = greater dispersion
• Standarddeviation--”average” difference
between the mean of a sample and each data
value in the sample
14+ 2.51 = Mean of 14 and SD of 2.51
Distribution...

...all adult men in Laramie, Wyoming.
b) all residential addresses in Laramie, Wyoming.
c) the members of the marketing firm that actually conducted the survey.
d) the 100 addresses to which the survey was mailed.
7. The chance that all 100 homes in a particular neighborhood in Laramie end up being the sample of residential addresses selected is
a) the same as for any other set of 100 residential addresses.
b) exactly 0. Simple random samples will spread out the addresses selected.
c) reasonably large due to the “cluster” effect.
d) 100 divided by the size of the population of Laramie.
Costs for standard veterinary services at a local animal hospital follow a Normal distribution with a mean of $80 and a standarddeviation of $20. Answer the next three questions.
8. Give the sample space for the costs of standard veterinary services.
a) {X ≥ 0}
b) { 0 ≤ X ≤ 80}
c) {0 ≤ X ≤ 160}
d) None of these.
9. What is the probability that one bill for veterinary services costs less than $95?
a) 0.75
a) 0.7734
b) 0.2266
c) 0.15
10. What is the probability that one bill for veterinary services costs between $75 and $105?
a) 1
a) 0.25
b) 0.4013
c) 0.4931
11. In an instant lottery, your chances of winning are 0.2. If you play the lottery five times and outcomes are independent, what is the probability that you win at least once?...

...the new point on the standarddeviation?
The new point has made the standarddeviation to go up to over 2.07
b) Follow the instructions to create the next two graphs then answer the following question: What did you do differently to create the data set with the larger standarddeviation.
What I did differently was to have two outliners on both ends of the outline so I can create the largerstandarddeviation and also to keep the mean at five.
2. Go back to the applet and put points matching each of the following data set into the first graph of the applet and clear the other two graphs. Set the lower limit to 0 and the upper limit to 100.
50, 50, 50, 50, 50
Notice that the standarddeviation is 0. Explain why the standarddeviation for this one is zero. Don’t show just the calculation. Explain in words why the standarddeviation is zero when all of the points are the same.
There’s not a deviation from this sample because all the data points are equal to each other.
3. Go back to the applet one last time and set all 3 of the lower limits to 0 and upper limits to 100. Then put each of the following three data sets into one of the graphs.
Data set 1: 0, 25, 50, 75, 100
Data set 2: 30, 40, 50, 60,...

...Problem Sheet - I
1. Researcher conducted by a tobacco company indicates that the relative frequency distribution of tar content of its newly developed low-tar cigarette has a mean equal to 3.9 milligrams of tar per cigarette and a standarddeviation equal to 1.0 milligram. Suppose a sample of 100 low-tar cigarettes is randomly selected from a day’s production and the tar content is measured in each. Assuming that the tobacco company’s claim is true, what is the probability that the mean tar content of the sample is greater than 4.15 milligrams?
[0.00621]
2. The safety limit of a crane is known to be 32 tons. The mean weight and the standarddeviation of a large number of iron rods are 0.3 ton and 0.2 ton respectively. One hundred rods are lifted at a time. Compute the probability of an accident.
[0.1587]
3. A soft –drink vending machine is set so that the amount of drink dispensed is a random variable with a mean of 200 milliliters and a standarddeviation of 15 milliliters. What is the probability that the mean amount dispensed in a random sample of size 36 is at least 204 milliliters?
[0.0548]
4. An automatic machine in a manufacturing process is operating properly if the lengths of an important subcomponent are normally distributed with mean (μ) = 117 cm and standarddeviation (σ) =...

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