When salespeople, construction supervisors, managers, and other employees are away from the workplace, many of them carry mobile devices such as laptop computers and PDAs, often containing valuable, private data related to their jobs. Pointsec (http://www.checkpoint. com/pointsec) provides security systems to protect such data. To bring home the vulnerability of mobile devices, Pointsec decided to share information about the number of such devices left behind in taxis.8 The research involved conducting a survey of taxi drivers. Staff members at Pointsec’s public relations firm called major taxi companies in nine cities in Australia, Denmark, Finland, France, Germany, Norway, Sweden, Great Britain, and the United States. Each of the cooperating companies put these interviewers in touch with about one hundred drivers. Drivers were asked how many devices of each type—cell phones, PDAs, computers, and so on—had been left in their cab over the preceding six months. From these numbers, they came up with the rate of items left behind.
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.
Case 17.1 Pointsec Mobile Technologies
When salespeople, construction supervisors, managers, and other employees are away from the workplace, many of them carry mobile devices such as laptop computers and PDAs, often containing valuable, private data related to their jobs. Pointsec (http://www.checkpoint. com/pointsec) provides security systems to protect such data. To bring home the vulnerability of mobile devices, Pointsec decided to share information about the number of such devices left behind in taxis.8 The research involved conducting a survey of taxi drivers. Staff members at Pointsec’s public relations firm called major taxi companies in nine cities in Australia, Denmark, Finland, France, Germany, Norway, Sweden, Great Britain, and the United States. Each of the cooperating companies put these interviewers in touch with about one hundred drivers. Drivers were asked how many devices of each type—cell phones, PDAs, computers, and so on—had been left in their cab over the preceding six months. From these numbers, they came up with the rate of items left behind. Multiplying by the size of taxi fleets in each city, the researchers came up with city-by-city numbers: 3.42 cell phones per cab yielded 85,619 cell phones left behind in Chicago, for example. In London, the researchers concluded 63,135 cell phones were left in cabs, a startling increase of 71 percent compared to four years earlier.
- Please provide an explanation of the confidence interval and confidence level.
- Determine in what situations you can use the z statistic to construct a confidence interval for the mean of a population.
- Verify what test statistic is used for constructing a confidence interval on the population’s proportion.
- Describe why and when t statistic is used in constructing a confidence interval for the mean of a population.
- Read the case study “Pointsec Mobile Technology” on page 439 of Zikmund et al. textbook (Chapter 17) and provide detailed answers to the questions asked.
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