Question

Flexural strength is a measure of a material's ability to resist failure in bending. The accompanying data are on flexural strength of concrete (in MegaPascal, MPa, where 1 Pa (Pascal) = 1.45 ⨯ 10−4 psi):

5.9 7.2 7.3 6.1 8.1 6.8 7.0 7.6 6.8 6.5 7.0 6.3 7.9 9.0

8.2 8.7 7.8 9.7 7.4 7.7 9.7 7.8 7.7 11.6 11.4 11.8 10.7

**(a) Construct a stem-and-leaf display of the data.
(Enter numbers from smallest to largest separated by spaces. Enter
NONE for stems with no values.)**

Stems / Leaves

5

6

7

8

9

10

11

**What appears to be a representative strength value?
MPa**

**Do the observations appear to be highly concentrated
about the representative value or rather spread out?**

highly concentrated around the representative value

spread out with a large range

**b) Does the display appear to be reasonably symmetric
about a representative value, or would you describe its shape in
some other way?**

reasonably symmetric

positive skewness

negative skewness

completely random distribution

**(c) Do there appear to be any outlying strength
values?**

Yes

No

**d) What proportion of strength observations in this
sample** **exceed** **10 MPa? (Round your
answer to two decimal places.)**

Answer #1

Consider the accompanying data on flexural strength (MPa) for
concrete beams of a certain type.
11.8
6.3
7.1
9.7
6.5
8.1
6.8
8.7
6.8
7.0
7.8
7.4
10.7
9.0
7.7
5.4
6.3
7.9
7.7
7.0
8.7
7.3
11.6
11.3
7.2
8.2
9.7
a.)Calculate a point estimate of the population standard deviation
σ. [Hint: Σxi2 =
1862.79.]
b.)Calculate a point estimate of the population coefficient of
variation σ/μ.

Consider the accompanying data on flexural strength (MPa) for
concrete beams of a certain type. 6.3 0.7 8.2 9.7 7.0 7.2 6.8 6.3
7.7 7.4 9.0 8.7 5.7 6.5 6.8 7.8 7.7 11.8 7.5 11.6 7.8 8.1 9.7 7.9
7.3 11.3 7.0 a) Calculate a point estimate of the mean value of
strength for the conceptual population of all beams manufactured in
this fashion. [Hint: ?xi = 219.5.] (Round your answer to three
decimal places.) MPa State which estimator you...

Consider the accompanying data on flexural strength (MPa) for
concrete beams of a certain type.
5.8
7.2
7.3
6.3
8.1
6.8
7.0
7.4
6.8
6.5
7.0
6.3
7.9
9.0
8.4
8.7
7.8
9.7
7.4
7.7
9.7
8.1
7.7
11.6
11.3
11.8
10.7
The data below give accompanying strength observations for
cylinders.
6.8
5.8
7.8
7.1
7.2
9.2
6.6
8.3
7.0
8.5
7.5
8.1
7.4
8.5
8.9
9.8
9.7
14.1
12.6
11.8
Prior to obtaining data, denote the beam strengths by...

Consider the accompanying data on flexural strength (MPa) for
concrete beams of a certain type.
6.0
7.2
7.3
6.3
8.1
6.8
7.0
7.1
6.8
6.5
7.0
6.3
7.9
9.0
8.3
8.7
7.8
9.7
7.4
7.7
9.7
8.1
7.7
11.6
11.3
11.8
10.7
The data below give accompanying strength observations for
cylinders.
6.2
5.8
7.8
7.1
7.2
9.2
6.6
8.3
7.0
9.0
8.0
8.1
7.4
8.5
8.9
9.8
9.7
14.1
12.6
11.3
Prior to obtaining data, denote the beam strengths by...

Consider the accompanying data on flexural strength (MPa) for
concrete beams of a certain type
6.0 7.2 7.3 6.3 8.1 6.8 7.0 7.5 6.8 6.5 7.0 6.3 7.9 9.0 9.0 8.7
7.8 9.7 7.4 7.7 9.7 8.2 7.7 11.6 11.3 11.8 10.7
The data below give accompanying strength observations for
cylinders.
6.1 5.8 7.8 7.1 7.2 9.2 6.6 8.3 7.0 8.5 7.5 8.1 7.4 8.5 8.9 9.8
9.7 14.1 12.6 11.9
Prior to obtaining data, denote the beam strengths by...

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