Question

At wind speeds above 1000 centimeters per second (cm/sec),
significant sand-moving events begin to occur. Wind speeds below
1000 cm/sec deposit sand and wind speeds above 1000 cm/sec move
sand to new locations. The cyclic nature of wind and moving sand
determines the shape and location of large dunes. At a test site,
the prevailing direction of the wind did not change noticeably.
However, the velocity did change. Sixty-two wind speed readings
gave an average velocity of *x* = 1075 cm/sec. Based on
long-term experience, *σ* can be assumed to be 240
cm/sec.

(a) Find a 95% confidence interval for the population mean wind speed at this site. (Round your answers to the nearest whole number.)

lower limit _________ cm/sec

upper limit _________ cm/sec

(b) Does the confidence interval indicate that the population mean wind speed is such that the sand is always moving at this site? Explain.

- No. This interval indicates that the population mean wind speed is such that the sand may not always be moving at this site.
- Yes. This interval indicates that the population mean wind speed is such that the sand may not always be moving at this site.
- Yes. This interval indicates that the population mean wind speed is such that the sand is always moving at this site.
- No. This interval indicates that the population mean wind speed is such that the sand is always moving at this site.

Answer #1

**Solution**

(a) The Z value for 95% CI is 1.96( taken out from Z tables)

The CI is given by :

Xbar +/- Z*Sigma/Sqrt(n)

= 1075 +/- 1.96*240/sqrt(62) = 1015 to 1135.

**Upper bounds = 1135, Lower bound of CI is
1015**

b) **Since even the lower bound is above 1000**(
1015 cm/sec > 1000cm/sec), the CI indicates that the population
mean wind speed is such that the sand is always moving at this
site.

**Yes. This interval indicates that the population mean
wind speed is such that the sand is always moving at this
site.**” (Option C_

At wind speeds above 1000 centimeters per second (cm/sec),
significant sand-moving events begin to occur. Wind speeds below
1000 cm/sec deposit sand and wind speeds above 1000 cm/sec move
sand to new locations. The cyclic nature of wind and moving sand
determines the shape and location of large dunes. At a test site,
the prevailing direction of the wind did not change noticeably.
However, the velocity did change. Sixty-five wind speed readings
gave an average velocity of x = 1075...

At wind speeds above 1000 centimeters per second (cm/sec),
significant sand-moving events begin to occur. Wind speeds below
1000 cm/sec deposit sand and wind speeds above 1000 cm/sec move
sand to new locations. The cyclic nature of wind and moving sand
determines the shape and location of large dunes. At a test site,
the prevailing direction of the wind did not change noticeably.
However, the velocity did change. Sixty-five wind speed readings
gave an average velocity of x = 1075...

At wind speeds above 1000 centimeters per second (cm/sec),
significant sand-moving events begin to occur. Wind speeds below
1000 cm/sec deposit sand and wind speeds above 1000 cm/sec move
sand to new locations. The cyclic nature of wind and moving sand
determines the shape and location of large dunes. At a test site,
the prevailing direction of the wind did not change noticeably.
However, the velocity did change. Sixty wind speed readings gave an
average velocity of x = 1075...

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