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A simple random sample of 400 households is taken in a large city, and the number of cars in each sampled household is noted. The average number of cars in the sampled households is 1.8 and the SD is 1.3. Among the sampled households, 10% had no car. PROBLEM 5 This problem is worth 1 point An approximate 90% confidence interval for the average number of cars among households in the city goes from _____________________ to _______________________.

  • 8 months ago
  • 8 months ago

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  1. ybarrap
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    \[\mu \pm z\alpha\] you already have average and standard deviation, what is "z" corresponding to 90th confidence interval?

    • 8 months ago
  2. ybarrap
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    The z that gives 90% confidence interval is 1.645: http://www.wolframalpha.com/input/?i=inverse+normal+z%3D1.645

    • 8 months ago
  3. ybarrap
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    \[1.8\pm1.645*1.3\] \[Lower Range: 1.8-1.645*1.3\] \[Upper Range: 1.8+1.645*1.3\] Does this make sense?

    • 8 months ago
  4. Social
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    @ybarrap What about this? An approximate 99% confidence interval for the percent of city households that have no car goes from _____________________% to ______________________%.

    • 8 months ago
  5. francoj22
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    6,14% to 13,86% ?

    • 8 months ago
  6. francoj22
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    Confidence Interval For Proportions

    • 8 months ago
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