Assume that the readings at freezing on a batch of thermometers are normally distributed with a mean of 0°C and a standard deviation of 1.00°C. A single thermometer is randomly selected and tested.

If 2.5% of the thermometers are rejected because they have readings that are too high and another 2.5% are rejected because they have readings that are too low, find the two readings that are cutoff values separating the rejected thermometers from the others.

Respuesta :

Using the normal distribution, it is found that the two readings that are cutoff values separating the rejected thermometers from the others are -1.96ºC and 1.96ºC.

Normal Probability Distribution

The z-score of a measure X of a normally distributed variable with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex] is given by:

[tex]Z = \frac{X - \mu}{\sigma}[/tex]

  • The z-score measures how many standard deviations the measure is above or below the mean.
  • Looking at the z-score table, the p-value associated with this z-score is found, which is the percentile of X.

The mean and the standard deviation are given, respectively, by:

[tex]\mu = 0, \sigma = 1[/tex].

The z-score that cuts off the bottom and top 2.5% of the distribution is [tex]z = \pm 1.96[/tex], hence:

[tex]Z = \frac{X - \mu}{\sigma}[/tex]

[tex]-1.96 = \frac{X - 0}{1}[/tex]

X = -1.96

[tex]Z = \frac{X - \mu}{\sigma}[/tex]

[tex]1.96 = \frac{X - 0}{1}[/tex]

X = 1.96

The two readings that are cutoff values separating the rejected thermometers from the others are -1.96ºC and 1.96ºC.

More can be learned about the normal distribution at https://brainly.com/question/27879230

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