Various Regions: Daily Positive COVID-19 Tests per 100 000 Population (explanations below)
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What does this chart show?
The chart shows the UK Government's data for lab-confirmed (see below) positive COVID-19 tests on each day in each of the chosen local authority areas. The underlying data are downloaded daily from the UK Government's website.

Data for different geographic areas (see below) are shown in different colours. You can choose which areas to show by clicking on the buttons next to its name. The colour of each button is the colour of the corresponding curve. We also included a button to show the University of Cambridge's own test data of their staff and students; this is discussed in more detail on the City and University numbers page.

For each day and each area (except Cambridge University, whose curve is discussed in more detail on the University-specific page), the graph shows average (see below) daily new positive lab tests per 100000 population. This allows direct comparison of data between large areas such as the whole of England and small ones such as Cambridge.

What does "lab-confirmed" mean?
For data up to 2 July 2020, the data only include positive tests taken at hospitals for those with a clinical need and for health care workers. Thereafter, test results for the wider population are also included, but only if processed by a lab.
This means that data from July onwards should not be directly compared to those from the March-June lock-down.

(Hospitalisation figures might be a better indicator if you wish to compare the severities of infection waves.)

What are the "areas" shown?
Most of these are officially designated administrative regions, counties and local authority areas in England. There are three exceptions:
  1. "The North" shows combined data for the North West, the North East, Yorkshire and The Humber, i.e. the entire North of England. Similarly for "The Midlands".
  2. "Greater Cambridge" shows the combined data for the City of Cambridge and surrounding South Cambridgshire. Thus, it represents the people you are most likely to meet at Tesco Bar Hill or, for that matter, at Addenbrookes Hospital!
  3. "Cambridge (actual cases)", which is the little crosses, shows the actual govenrment data for new Cambridge cases on each day. Since the population of Cambridge is 124000, these are on average 25% above the red curve which shows cases per 100000.
  4. "Cambridge University" shows the results of the tests taken on behalf of Cambridge University for those of their staff and students who show Covid-19 symptoms. These, in turn, are part of the data for either Cambridge City or, if staff live there, for South Cambridgeshire. More details about these tests are on the page.
Averages
For each day, the average of the data for the seven days around that day are shown. This serves to smooth out fluctuations in testing, lab work and reporting over the course of a week.

In addition, the data points are smoothed further over three neighbouring days. This serves to smooth out statistical fluctuations in the data due to too small a sample.

Very recent data
Data for the last few days shown on each graph are not final: test results typically arrive between 1-4 days after the tests are taken. Thus the last data point, as reported each day by the government, is so haphazard that we dropped it completely. Before that, we found by detailed analysis that typical mid-week reports arrive at about 95% of the final numbers after two days, 99% after three, and usually at the final number after four days. We tried to take this into account with corresponding corrections of the raw data for the last few days on each curve. (On weekends, however, these reporting delays seem to be longer; accordingly, if you look at these graphs in the middle of a week, a fake dip for the preceeding weekend may appear at the end of each curve.)
"Per 100000"
For each area, we used population numbers from various sources. The numbers are:
    
    
    
    
    
    
    
    
    
    
    
(City Council, verbal communication)
    
    
    
    
    
Important Caveats
Not included in the data, and hence in the graphs, are: