Solving Probability Questions: Mean & CI Estimate

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SUMMARY

The discussion focuses on estimating the mean setting time of a new cement mix used in highway spot repairs, based on recorded times from 10 spot repairs. The recorded times are 25, 25, 24, 23, 25, 26, 23, 24, 22, and 23 minutes. Participants are tasked with calculating the mean and standard deviation, as well as determining 95% confidence intervals for the mean setting time under both known and unknown standard deviation scenarios. The known standard deviation is specified as 1.5 minutes.

PREREQUISITES
  • Understanding of basic statistics, including mean and standard deviation
  • Familiarity with confidence intervals and their significance
  • Knowledge of normal distribution properties
  • Ability to perform calculations using statistical formulas
NEXT STEPS
  • Calculate the mean and standard deviation of the provided setting times
  • Learn how to compute a 95% confidence interval using known standard deviation
  • Explore methods for calculating confidence intervals when standard deviation is unknown
  • Study the implications of normal distribution in statistical analysis
USEFUL FOR

Engineers, statisticians, and students who are involved in quality control, data analysis, or any field requiring statistical estimation and confidence interval calculations.

sinni8
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probability questions please help!

An engineer wishes to estimate the mean setting time of
a new cement mix used in highway spot repairs. From a record of setting times
for 10 spot repairs he obtain
x = 25; 25; 24; 23; 25; 26; 23; 24; 22; 23
minutes, respectively.
(a) Find the mean and standard deviation of the setting time.

(b) Find a 95% confidence interval for the mean setting time if the standard deviation
is known to be ¾ = 1:5 min: Assume a normal distribution
(c) Find a 95% confidence interval for for the mean setting time if the standard
deviation is unknown.
 
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Welcome to PF!

sinni8 said:
An engineer wishes to estimate the mean setting time of
a new cement mix used in highway spot repairs. From a record of setting times
for 10 spot repairs he obtain
x = 25; 25; 24; 23; 25; 26; 23; 24; 22; 23
minutes, respectively.
(a) Find the mean and standard deviation of the setting time.

(b) Find a 95% confidence interval for the mean setting time if the standard deviation
is known to be ¾ = 1:5 min: Assume a normal distribution
(c) Find a 95% confidence interval for for the mean setting time if the standard
deviation is unknown.

Hi sinni8! Welcome to PF! :smile:

Show us what you've tried, and where you're stuck, and then we'll know how to help. :smile:
 

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