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-one wind speed readings gave an average velocity of x = 1075 cm/sec. Based on long-term experience, σ can be assumed to be 250 cm/sec.

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

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

Answer 1

Since population standard deviation is known, Use z-distribution.

Refer Standard normal table/Z-table or use excel function "=NORM.S.INV((1-0.025))" to find the critical value of z.