Mean from a Histogram The histogram shows the lengths of index fingers (in millimeters) for a sample of eighth-graders. (Source: AMSTAT Census at School) a. Use the histogram to approximate the mean ring finger length for the sample. b. Approximate the mean by completing the work that is started below. Note that the left-hand side of each bin is being used in this approximation: x ¯ = 3 60 + 9 70 + 5 80 + … 27 c. Explain why the method used in part (b) is an approximation of the mean rather than the actual mean.
Mean from a Histogram The histogram shows the lengths of index fingers (in millimeters) for a sample of eighth-graders. (Source: AMSTAT Census at School) a. Use the histogram to approximate the mean ring finger length for the sample. b. Approximate the mean by completing the work that is started below. Note that the left-hand side of each bin is being used in this approximation: x ¯ = 3 60 + 9 70 + 5 80 + … 27 c. Explain why the method used in part (b) is an approximation of the mean rather than the actual mean.
Mean from a Histogram The histogram shows the lengths of index fingers (in millimeters) for a sample of eighth-graders. (Source: AMSTAT Census at School)
a. Use the histogram to approximate the mean ring finger length for the sample.
b. Approximate the mean by completing the work that is started below. Note that the left-hand side of each bin is being used in this approximation:
x
¯
=
3
60
+
9
70
+
5
80
+
…
27
c. Explain why the method used in part (b) is an approximation of the mean rather than the actual mean.
Definition Definition Measure of central tendency that is the average of a given data set. The mean value is evaluated as the quotient of the sum of all observations by the sample size. The mean, in contrast to a median, is affected by extreme values. Very large or very small values can distract the mean from the center of the data. Arithmetic mean: The most common type of mean is the arithmetic mean. It is evaluated using the formula: μ = 1 N ∑ i = 1 N x i Other types of means are the geometric mean, logarithmic mean, and harmonic mean. Geometric mean: The nth root of the product of n observations from a data set is defined as the geometric mean of the set: G = x 1 x 2 ... x n n Logarithmic mean: The difference of the natural logarithms of the two numbers, divided by the difference between the numbers is the logarithmic mean of the two numbers. The logarithmic mean is used particularly in heat transfer and mass transfer. ln x 2 − ln x 1 x 2 − x 1 Harmonic mean: The inverse of the arithmetic mean of the inverses of all the numbers in a data set is the harmonic mean of the data. 1 1 x 1 + 1 x 2 + ...
Morningstar tracks the total return for a large number of mutual funds. The following table shows the total return and the number of funds for four categories of mutual funds.
Click on the datafile logo to reference the data.
DATA file
Type of Fund
Domestic Equity
Number of Funds
Total Return (%)
9191
4.65
International Equity
2621
18.15
Hybrid
1419
2900
11.36
6.75
Specialty Stock
a. Using the number of funds as weights, compute the weighted average total return for these mutual funds. (to 2 decimals)
%
b. Is there any difficulty associated with using the "number of funds" as the weights in computing the weighted average total return in part (a)? Discuss. What else might be used for weights?
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c. Suppose you invested $10,000 in this group of mutual funds and diversified the investment by placing $2000 in Domestic Equity funds, $4000 in International Equity funds, $3000 in Specialty Stock…
The days to maturity for a sample of five money market funds are shown here. The dollar amounts invested in the funds are provided.
Days to
Maturity
20
Dollar Value
($ millions)
20
12
30
7
10
5
6
15
10
Use the weighted mean to determine the mean number of days to maturity for dollars invested in these five money market funds (to 1 decimal).
days
c. What are the first and third quartiles?
First Quartiles (to 1 decimals)
Third Quartiles (to 4 decimals)
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Which companies spend the most money on advertising? Business Insider maintains a list of the top-spending companies. In 2014, Procter & Gamble spent more than any other company, a whopping $5 billion. In second place was Comcast, which spent $3.08 billion (Business Insider website, December 2014). The top 12 companies and
the amount each spent on advertising in billions of dollars are as follows.
Click on the datafile logo to reference the data.
DATA file
Company
Procter & Gamble
Comcast
Advertising
($billions)
$5.00
3.08
2.91
Company
American Express
General Motors
Advertising
($billions)
$2.19
2.15
ETET
AT&T
Ford
Verizon
L'Oreal
2.56
2.44
2.34
Toyota
Fiat Chrysler
Walt Disney Company
J.P Morgan
a. What is the mean amount spent on advertising? (to 2 decimals)
2.55
b. What is the median amount spent on advertising? (to 3 decimals)
2.09
1.97
1.96
1.88
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