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# point estimate formula

From Wikipedia

Point estimation

In statistics, point estimation involves the use of sampledata to calculate a single value (known as a statistic) which is to serve as a "best guess" for an unknown (fixed or random) population parameter.

More formally, it is the application of a point estimator to the data.

In general, point estimation should be contrasted with interval estimation.

Point estimation should be contrasted with general Bayesian methods of estimation, where the goal is usually to compute (perhaps to an approximation) the posterior distributions of parameters and other quantities of interest. The contrast here is between estimating a single point (point estimation), versus estimating a weighted set of points (a probability density function). However, where appropriate, Bayesian methodology can include the calculation of point estimates, either as the expectation or median of the posterior distribution or as the mode of this distribution.

In a purely frequentist context (as opposed to Bayesian), point estimation should be contrasted with the specific interval estimation calculation of confidence intervals.

## Properties of Point estimates

Construction Estimating Software

Construction estimating software is computer software designed for contractors to estimate construction costs for a specific project. A contractor will typically use estimating software to estimate his bid price for a project owner, which will ultimately become part of a resulting construction contract. Some architects and engineers may also use estimating softare, but usually only to provide a budgetary cost estimate to an owner prior to construction.

## History

Contractors review a project's plans and specifications to produce a takeoff (a list of item and material quantities needed for the project). This is traditionally done by analyzing the project plans and, utilizing knowledge of required construction methods, producing an itemized list of the project requirements. Then, based on this list, a contractor will tabulate the various resources and costs for every aspect of construction. There are many ways to estimate with so many different programs. These resource costs include labor, equipment, materials, subcontractors, and any other related costs.

With the advent of computers in business, contractors began using spreadsheet applications like VisiCalc, Lotus 1-2-3, and Microsoft Excel to duplicate the traditional tabular format, while automating redundant mathematical formulas.

As the popularity of spreadsheets has grown, exchanges are starting to appear where professional estimators can buy or sell construction estimating spreadsheets that they have created. see http://www.estimatingtemplates.com for example.

### Database Applications Emerge

As more and more contractors came to rely on spreadsheets, and the formulas within the spreadsheets became more complex, spreadsheet errors became more frequent. These were typically formula errors and cell-reference errors. Hard-coded formulas in database applications were originally created to overcome these errors. As these applications became more and more popular over the years, additional features, such as saving data for reuse and trade-specific calculations, have become available.

Many of these software applications are specific to different construction markets, such as residential building, remodeling, masonry, electrical, and heavy construction. Today most contractors use Microsoft Project and Primavera. For example, programs like Sage Timberline Office and MasterBuilder, that are designed for building construction, include libraries and program features for traditional builders. In sharp contrast, programs like HCSS HeavyBid and SharpeSoft Estimator, that are designed for civil construction, include libraries and program features for roadway, utility, and bridge builders.

Like most other business applications, estimating programs typically run on Microsoft Windows-based computers, but some, such as Turtlesoft Goldenseal, will also run on Macintosh computers.

## Typical Software Features

• Item or Activity List: All estimating software applications will include a main project window that outlines the various items or activities that will be required to complete the specified project. More advanced programs are capable of breaking an item up into subtasks, or sublevels. An outline view of all of the top-level and sub-level items provides a quick and easy way to view and navigate through the project.
• Resource Costs: Resources consist of labor, equipment, materials, subcontractors, trucking, and any other cost detail items. Labor and equipment costs are internal crew costs, whereas all other resource costs are received from vendors, such as material suppliers, subcontractors, and trucking companies. Labor costs are usually calculated from wages, benefits, burden, and workers compensation. Equipment costs are calculated from purchase price, taxes, fuel consumption, and other operating expenses.
• Item or Activity Detail: The detail to each item includes all of the resources required to complete each activity, as well as their associated costs. Production rates will automatically determine required crew costs.
• Calculations: Most estimating programs have built-in calculations ranging from simple length, area, and volume calculations to complex industry-specific calculations, such as electrical calculations, utility trench calculations, and earthwork cut and fill calculations.
• Markups: Every program will allow for cost mark-ups ranging from flat overall mark-ups to resource-specific mark-ups, mark-ups for general administrative costs, and bonding costs.
• Detailed Overhead: Indirect costs, such as permits, fees, and any other overall project costs can be spread to project items.
• Closeout Window: Many estimating programs include a screen for manually adjusting bid prices from their calculated values.
• Reporting: Project reports typically include proposals, detail reports, cost breakdown reports, and various charts and graphs.
• Exporting: Most software programs can export project data to other applications, such as spreadsheets, accounting software, and project management software.
• Job History: Storing past projects is a standard feature in most estimating programs.

Question:Hi, need a little help with a stat problem please. A data set has a sample size of 61, sample average of 11.7, an a standard deviation of 3.8 What is the point estimate of the population mean? Compute a 92% confidence interval for the population mean. Thanks!

Answers:hmm..if i'm not mistaken, the point estimate of the population mean is the sample mean = 11.7 92% confidence interval: 11.7 (1.75)(3.8/[ 61]) =11.7 0.851445 =(10.8486,12.5514) Assumptions: 1) Random sample is selected from target population 2) Sample size n is large ----n=61>30

Question:A simple random sample of 8 employees is selected from a large firm. For the 8 employees, the number of days each was absent during the past month was found to be 2, 2, 3, 4, 2, 8, 2, and 3. What is the point estimate for , the mean number of days absent for the firm's employees? Round to nearest hundredth. What is the point estimate for , the variance of the number of days absent? Round to nearest

Answers:point estimate for the mean would be the sample mean (add them all up and divide by 8). Point estimate for the standard deviation is sample standard deviation divided by sqrt(8). Square that for the variance. That would be your point estimate.

Question:Private colleges and universities rely on money contributed by individuals and corporations for their operating expenses. Much of this money is put into a fund called an endowment, and the college spends only the interest earned by the fund. A recent survey of eight private colleges in the United States revealed the following endowments (in millions of dollars): 74.8, 53.3, 242.2, 499.2, 124.7, 151.2, 92.7, and 211.4. What value will be used as the point estimate for the mean endowment of all private colleges in the United States?

Answers:point estimate for the mean endowment of all private colleges in the United States = 181.19

Question:

Answers:actually you don't do point estimates for statistics. statistics are values that are taken from a sample and are actual data. point estimate refers to parameters, information about the population. typically the statistic is a point estimate (a single value estimate) for the parameter. this is different from a confidence interval which gives you a range of values for the parameter.