Confidence intervals for a mean · Short practice

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Recall

Normal confidence intervals — objective 1

Maths4U Original · Short practice

A normal population has known standard deviation 7. An independent random sample of size 25 has mean 49. Use a two-sided 95% confidence interval, with \(\displaystyle z=1.95996398454\).

Find the interval half-width.

Enter one number or fraction. Use at least six decimal places when needed; a distribution calculator may be used for probabilities.

Fresh review variant

Normal confidence intervals — objective 1

Maths4U Original · Short practice

A normal population has known standard deviation 3. An independent random sample of size 36 has mean 50. Use a two-sided 95% confidence interval, with \(\displaystyle z=1.95996398454\).

Find the interval half-width.

Enter one number or fraction. Use at least six decimal places when needed; a distribution calculator may be used for probabilities.

Method

Normal confidence intervals — objective 2

Maths4U Original · Short practice

A normal population has known standard deviation 3. An independent random sample of size 36 has mean 50. Use a two-sided 95% confidence interval, with \(\displaystyle z=1.95996398454\).

Find the lower endpoint.

Enter one number or fraction. Use at least six decimal places when needed; a distribution calculator may be used for probabilities.

Fresh review variant

Normal confidence intervals — objective 2

Maths4U Original · Short practice

A normal population has known standard deviation 4. An independent random sample of size 49 has mean 51. Use a two-sided 95% confidence interval, with \(\displaystyle z=1.95996398454\).

Find the lower endpoint.

Enter one number or fraction. Use at least six decimal places when needed; a distribution calculator may be used for probabilities.

Apply

Normal confidence intervals — objective 3

Maths4U Original · Short practice

A normal population has known standard deviation 4. An independent random sample of size 49 has mean 51. Use a two-sided 95% confidence interval, with \(\displaystyle z=1.95996398454\).

Find the upper endpoint.

Enter one number or fraction. Use at least six decimal places when needed; a distribution calculator may be used for probabilities.

Fresh review variant

Normal confidence intervals — objective 3

Maths4U Original · Short practice

A normal population has known standard deviation 5. An independent random sample of size 16 has mean 52. Use a two-sided 95% confidence interval, with \(\displaystyle z=1.95996398454\).

Find the upper endpoint.

Enter one number or fraction. Use at least six decimal places when needed; a distribution calculator may be used for probabilities.

Check understanding

Normal confidence intervals — objective 4

Maths4U Original · Short practice

A normal population has known standard deviation 5. An independent random sample of size 16 has mean 52. Use a two-sided 95% confidence interval, with \(\displaystyle z=1.95996398454\).

Find the minimum sample size for half-width at most 1.2, using the same σ and confidence level.

Enter one number or fraction. Use at least six decimal places when needed; a distribution calculator may be used for probabilities.

Fresh review variant

Normal confidence intervals — objective 4

Maths4U Original · Short practice

A normal population has known standard deviation 6. An independent random sample of size 25 has mean 53. Use a two-sided 95% confidence interval, with \(\displaystyle z=1.95996398454\).

Find the minimum sample size for half-width at most 1.25, using the same σ and confidence level.

Enter one number or fraction. Use at least six decimal places when needed; a distribution calculator may be used for probabilities.

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