Kevlar epoxy is a material used on the NASA space shuttles. Strands of this epoxy were tested at the 90% breaking strength. The following data represent time to failure (in hours) for a random sample of 50 epoxy strands. Let x be a random variable representing time to failure (in hours) at 90% breaking strength. 0.53 1.80 1.52 2.05 1.03 1.18 0.80 1.33 1.29 1.13 3.34 1.54 0.08 0.12 0.60 0.72 0.92 1.05 1.43 3.01 1.81 2.17 0.63 0.56 0.03 0.09 0.18 0.34 1.51 1.45 1.52 0.19 1.55 0.01 0.07 0.65 0.40 0.24 1.51 1.45 1.60 1.80 4.69 0.08 7.89 1.58 1.62 0.03 0.23 0.72 (a) Find the range. (b) Use a calculator to calculate Σx and Σx2. Σx = Σx2 = (c) Use the results of part (b) to compute the sample mean, variance, and standard deviation for the time to failure. (Round your answers to four decimal places.) x = s2 = s = (d) Use the results of part (c) to compute the coefficient of variation. (Round your answer to the nearest whole number.) % What does this number say about time to failure? The standard deviation of the time to failure is just slightly smaller than the average time.The coefficient of variation says nothing about time to failure. The standard deviation of the time to failure is just slightly larger than the average time.The standard deviation is equal to the average. Why does a small CV indicate more consistent data, whereas a larger CV indicates less consistent data? Explain. A small CV indicates more consistent data because the value of s in the numerator is smaller.A small CV indicates more consistent data because the value of s in the numerator is larger.
Addition Rule of Probability
It simply refers to the likelihood of an event taking place whenever the occurrence of an event is uncertain. The probability of a single event can be calculated by dividing the number of successful trials of that event by the total number of trials.
Expected Value
When a large number of trials are performed for any random variable ‘X’, the predicted result is most likely the mean of all the outcomes for the random variable and it is known as expected value also known as expectation. The expected value, also known as the expectation, is denoted by: E(X).
Probability Distributions
Understanding probability is necessary to know the probability distributions. In statistics, probability is how the uncertainty of an event is measured. This event can be anything. The most common examples include tossing a coin, rolling a die, or choosing a card. Each of these events has multiple possibilities. Every such possibility is measured with the help of probability. To be more precise, the probability is used for calculating the occurrence of events that may or may not happen. Probability does not give sure results. Unless the probability of any event is 1, the different outcomes may or may not happen in real life, regardless of how less or how more their probability is.
Basic Probability
The simple definition of probability it is a chance of the occurrence of an event. It is defined in numerical form and the probability value is between 0 to 1. The probability value 0 indicates that there is no chance of that event occurring and the probability value 1 indicates that the event will occur. Sum of the probability value must be 1. The probability value is never a negative number. If it happens, then recheck the calculation.
Kevlar epoxy is a material used on the NASA space shuttles. Strands of this epoxy were tested at the 90% breaking strength. The following data represent time to failure (in hours) for a random sample of 50 epoxy strands. Let x be a random variable representing time to failure (in hours) at 90% breaking strength.
| 0.53 | 1.80 | 1.52 | 2.05 | 1.03 | 1.18 | 0.80 | 1.33 | 1.29 | 1.13 |
| 3.34 | 1.54 | 0.08 | 0.12 | 0.60 | 0.72 | 0.92 | 1.05 | 1.43 | 3.01 |
| 1.81 | 2.17 | 0.63 | 0.56 | 0.03 | 0.09 | 0.18 | 0.34 | 1.51 | 1.45 |
| 1.52 | 0.19 | 1.55 | 0.01 | 0.07 | 0.65 | 0.40 | 0.24 | 1.51 | 1.45 |
| 1.60 | 1.80 | 4.69 | 0.08 | 7.89 | 1.58 | 1.62 | 0.03 | 0.23 | 0.72 |
(b) Use a calculator to calculate Σx and Σx2.
| Σx | = |
| Σx2 | = |
(c) Use the results of part (b) to compute the sample mean, variance, and standard deviation for the time to failure. (Round your answers to four decimal places.)
| x | = |
| s2 | = |
| s | = |
(d) Use the results of part (c) to compute the coefficient of variation. (Round your answer to the nearest whole number.)
%
What does this number say about time to failure?
Why does a small CV indicate more consistent data, whereas a larger CV indicates less consistent data? Explain.
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