CALIB Manual - Chapter 2

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Program Options

• File / New This is where sample data is entered from the keyboard. Once sample data has been entered, it can be modified by opening this dialog and adjusting the sample number to bring up the desired sample.
• File / Open If you have saved the sample data entered during a previous session, you can retrieve that information here. As an alternative to adding sample data from the keyboard, you can enter it in a template file and then read that data using this menu option.
• File / Save The contents of the topmost window are saved. If you are having trouble getting the calibration options or plots to save, try closing the sample input dialog, as that is usually the topmost window when it is open.
• File / Page Setup
• File / Print
• Options / Calibration
  • Precision: Results can be presented with one standard deviation precision, two standard deviations, or both.
  • Output: cal ranges can be be given in years BP or AD/BC, but not both.
  • Treatment of Lab Errors: This option controls the use of lab error as a multiplier or added variance. The standard deviation reported with a radiocarbon age is often based on count rate statistics only. The user must decide whether to use the quoted laboratory error, or increase the quoted error to account for other sources of variance by either applying a lab error multiplier k or adding variance f^2 Thus the sample standard deviation s becomes either k*s or (s^2 + f^2)/2. The calibration curve sigma is automatically added in both cases to give the total sigma of the radiocarbon age prior to its cal age transformation. A lab error multiplier is based on the overall reproducibility and should be supplied by the individual laboratory. The default is to use the lab error as a multiplier.
  • Sample Identification: can be by sample code or lab code
• Options / Sample Selection Samples may be disabled, or removed from consideration by the calibration routine or the tools, without actually deleting them. They can also be deleted here.
• Options / Plot Type There are two categories of plots: those with multiple samples per plot and those with only one. There are 3 types of multi-sample plots and 4 types of single-sample plots. The number of samples per multi-sample plot are controlled from the plot window itself.
• Options / Plot Axes The program makes an attempt at calculating sensible limits for the plot axes. If desired they can be set manually in this dialog. The manually set axes remain in effect as long as the dialog is open, and reverts to automatic calculation when the dialog is closed.
• Calibrate No calibration is done until this menu selection is made. Recalibration is necessary if options such as cal age format or number of standard deviations to display are changed.
• View / Plot This brings up a plot window showing a plot in the currently selected type. A postscript file named calib.eps is automatically created for each plot.
• Tools / Sample Ordering Sort samples by radiocarbon age, or, if they have a marine component, by radiocarbon age corrected with a Delta R value.
• Tools / Sample Significance Test if selected sample ages are estimating the same date (or effectively indistinguishably different dates) for replicate measurements ( Case 1 of Ward and Wilson (1978))
  • ttest is the test statistic which has a chi-square distribution with n-1 degrees of freedom under the null hypothesis.
  • ttest = sum from 1 to n (rage(i) - pooled_mean_age)**2/sigma(i)**2
• Tools / Create Pooled Mean Create a sample whose radiocarbon age is the pooled mean radiocarbon age of all selected samples. The pooled mean age is calculated by weighting (uncertainty * laberr) for several samples. The new sample is named 'AVERAGE'. It can be renamed in the File / New menu.
• Tools / Sum Probabilities This tool sums calibrated probability distributions by year and normalizes the area under the resulting distribution to 1. Samples must be calibrated before it becomes enabled. The interpretation of summed probability distributions is that it represents the probability that independent events A OR B occured at a particular time. If the probability of event A AND event B occuring at a particular time is desired then their probability distributions must be multiplied and the user is referred to a program like OXCAL or BCal. Summing probability distributions creates a new sample named 'SUM'. It can be renamed in the File / New menu.

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