With Covid-19 the numbers are coming at us all constantly. Every night there's an update, every day a further briefing. Many of us use the numbers of 'confirmed positives' to gauge how the country is handling the crisis.
But not every update is equal - on Tuesday and Wednesday of this week the first results for testing done under a new case definition will begin to emerge into the nightly numbers.
That will make it difficult for epidemiologists and statisticians to compare last week's updates to this week. The change in case definition focused testing on groups of people more likely to test positive than others.
According to the experts Prime Time spoke to, any day-to-day comparisons will need to come with a proviso, until we see how the