Tutorial solutions week 7

# so 9525 of households in the city

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Unformatted text preview: 95.25% of households in the city have annual incomes greater than \$30,000. ( ) ( ) ( ) ( ) Therefore we expect 0.5934×60≈36 households in the sample to have annual incomes between \$35,000 and \$45,000. 3. What is the 25th percentile of the normal distribution N(10, 9)? Hint: Find the value, z, of a standardized normal random variable, Z, that is such that ( ) and then ‘unstandardize’ to get the equivalent value for a N(10,9) variate. Let x be the required percentile. First find z, the 25th percentile of a standard normal. ( ( ) ( ) ( ) ) ( ) 4. In a certain city it is estimated that 40% of households have access to the internet. A company wishing to sell services to internet users randomly chooses 150 households in the city and sends them advertising material. For the households contacted: (a) Calculate the probability that less than 60 households have internet access? Let X be the number of households contacted that have internet access. Then assume X is a binomial rand...
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