Naval aircraft operate in a severe maritime environment. The proximity to seawater, spray and mist on board an aircraft carrier creates a corrosive severity up to 100 times more severe than land base environments. It is believed that if aircraft are rotated such that they spend less days deployed on a ship, the days necessary to repair corrosion in the depot can be reduced.

A study was undertaken where the schedule of a small number of aircraft were managed to ensure they spent less days on board an aircraft carrier between depot cycles. The 15 aircraft in the study are designated "Rotational Aircraft."

The purpose of the study was to determine if the aircraft in the study would require less days to repair corrosion compared to the population of aircraft.

To ascertain the test as successful, a 95% statistical significance is desired (p<0.05).

The average number of depot days for all aircraft that have been deployed on aircraft carriers is 117.62 days with a standard deviation of 5.2978. The distribution of this data is normally distributed. The data describing the depot days for the aircraft in this study is provided in the Table 1.

Use StatCrunch to analyze the shape of the data and derive necessary statistics.

Table 1

Days in Depot Data for Rotational Aircraft

	Days
	111
	110
	112
	113
	109
	112
	107
	111
	115
	110
	109
	113
	112
	110
	111

Z-Test Analysis

Perform a z-test hypothesis analysis. Show your work. At minimum, your analysis should include the following:

• An introduction
• A null and alternate hypothesis
• A histogram of the depot days for the rotational aircraft in the experiment(Create a histogram in Statcrunch with a Normal distribution overlay or use the slider function in Statcrunch to select a histogram that best approaches a normal distribution.)
• The skewness and kurtosis of the data
• Discuss the following: In your opinion, is the distribution of the data for the experiment normal. Why or why not?
• The z-critical value
• The z score from the analysis
• A decision about rejecting the null hypothesis based on comparing the z-critical value to the z-score.
• Based on the results and analysis of this z-test, write a conclusion that includes a description of the experiment, the hypothesis test used in the analysis, the size of the sample set, the confidence interval used, the z-critical score, the z-statistics score (z-stat), a comparison of the z-critical score to the z-stat, whether the null hypothesis was rejected, a conclusion of the experiment, and a statement about the statistical significance of the analysis