Statistics For Dummies, 2nd Edition

Confidence Level | z*– value |
---|---|

90% | 1.64 |

95% | 1.96 |

98% | 2.33 |

99% | 2.58 |

Moreover, what is the alpha value for a 90 confidence interval?

Area in Tails

Confidence Level | Area between 0 and z-score | Area in one tail (alpha/2) |
---|---|---|

90% | 0.4500 | 0.0500 |

95% | 0.4750 | 0.0250 |

98% | 0.4900 | 0.0100 |

99% | 0.4950 | 0.0050 |

What is the meaning of 95% confidence interval?

If repeated samples were taken and the

**95**%**confidence interval**was computed for each sample,**95**% of the**intervals**would contain the population**mean**. A**95**%**confidence interval**has a 0.95 probability of containing the population**mean**.**95**% of the population distribution is contained in the**confidence interval**.1

## What is the critical value for a 99 confidence interval?

Statistics For Dummies, 2nd Edition

Confidence Level | z*– value |
---|---|

90% | 1.64 |

95% | 1.96 |

98% | 2.33 |

99% | 2.58 |

2

## What is the critical value for a 94 confidence interval?

B. Common confidence levels and their critical values

Confidence Level | Critical Value (Z-score) |
---|---|

0.94 | 1.88 |

0.95 | 1.96 |

0.96 | 2.05 |

0.97 | 2.17 |

3

## What is the confidence level of 98?

Statistics For Dummies, 2nd Edition

Confidence Level | z*-value |
---|---|

90% | 1.645 (by convention) |

95% | 1.96 |

98% | 2.33 |

99% | 2.58 |

4

## What is the critical value?

In hypothesis testing, a

**critical value**is a point on the test distribution that is compared to the test statistic to determine whether to reject the null hypothesis. If the absolute**value**of your test statistic is greater than the**critical value**, you can declare statistical significance and reject the null hypothesis.5

## How do you know when to reject the null hypothesis?

Set the significance level, α, the probability of making a Type I error to be small — 0.01, 0.05, or 0.10. Compare the P-value to α. If the P-value is less than (or equal to) α,

**reject**the**null hypothesis**in favor of the alternative**hypothesis**. If the P-value is greater than α, do not**reject**the**null hypothesis**.6

## What is the standard normal table?

A

**standard normal table**, also called the unit**normal table**or Z**table**, is a mathematical**table**for the values of Φ, which are the values of the cumulative distribution function of the**normal**distribution.7

## Is the T procedures robust against outliers?

The

**t procedures**are**robust against**non-normality of the population when there are no**outliers**, especially when the distribution is roughly symmetric and unimodal. When is it appropriate**to**use the**t procedures**? n>15: The**t procedure**can be used except in the presence of**outliers**or strong skewness.8

## How do you find the z score for confidence intervals?

Step 1: Divide your

**confidence level**by 2: .95/2 = 0.475. Step 2: Look up the**value**you calculated in Step 1 in the**z**-table and**find**the corresponding**z**-**value**. The**z**-**value**that has an area of .475 is 1.96. Step 3: Divide the number of events by the number of trials to**get**the “P-hat”**value**: 24/160 = 0.15.9

## How do you find the point estimate?

Suppose that you want to

**find**out the average weight of all players on the football team at Landers College. You are able to select ten players at random and weigh them. The mean weight of the sample of players is 198, so that number is your**point estimate**. Assume that the population standard deviation is σ = 11.50.10

## What is a critical value in calculus?

In mathematics, a

**critical**point or stationary point of a differentiable function of a real or complex variable is any**value**in its domain where its derivative is 0. Some authors include in the**critical**points the limit points where the function may be prolongated by continuity and where the derivative is not defined.11

## How do we find the margin of error?

**Here are the steps for calculating the margin of error for a sample proportion:**

- Find the sample size, n, and the sample proportion.
- Multiply the sample proportion by.
- Divide the result by n.
- Take the square root of the calculated value.
- Multiply the result by the appropriate z*-value for the confidence level desired.

12

## What is Alpha in statistics and what does it mean?

**Alpha**is usually expressed as a proportion. Thus, if the confidence level is 95%, then

**alpha**would equal 1 - 0.95 or 0.05. With respect to hypothesis tests ,

**alpha**refers to significance level , the probability of making a Type I error .

13

## What is the z score for a 90 confidence interval?

Confidence Intervals

Desired Confidence Interval | Z Score |
---|---|

90% 95% 99% | 1.645 1.96 2.576 |

14

## How do you determine the degrees of freedom?

just create an account. For instance, if a sample size were 'n' on a chi-square test, then the number of

**degrees of freedom**to be used in**calculations**would be n - 1. To**calculate**the**degrees of freedom**for a sample size of N=9. subtract 1 from 9 (df=9-1=8).15

## What does ZC stand for in statistics?

A critical value often represents a rejection region cut-off value for a hypothesis test – also called a

**zc**value for a confidence interval. For confidence intervals and two-tailed z-tests, you can use the zTable to determine the critical values (**zc**).16

## What is the test statistic?

A

**test statistic**is a random variable that is calculated from sample data and used in a hypothesis**test**. You can use**test statistics**to determine whether to reject the null hypothesis. The sampling distribution of the**test statistic**under the null hypothesis is called the null distribution.17

## How do you find critical values in calculus?

To

**find**these**critical**points you must first take the derivative of the**function**. Second, set that derivative equal to 0 and solve for x. Each x**value**you**find**is known as a**critical**number. Third, plug each**critical**number into the original equation to obtain your y**values**.18

## How do you find the Z score?

To

**find the Z score**of a sample, you'll need to**find**the mean, variance and standard deviation of the sample. To calculate the**z**-**score**, you will**find**the difference between a**value**in the sample and the mean, and divide it by the standard deviation.19

## How z score is calculated?

Z-

**scores**are expressed in terms of standard deviations from their means. The formula for calculating the standard**score**is given below: As the formula shows, the standard**score**is simply the**score**, minus the mean**score**, divided by the standard deviation.20

## How do z scores work?

The standard

**score**(more commonly referred to as a**z**-**score**) is a very useful statistic because it (a) allows us to calculate the probability of a**score**occurring within our normal distribution and (b) enables us to compare two**scores**that are from different normal distributions.